SemOpenAlex |

SemOpenAlex

Matches in SemOpenAlex for { <https://semopenalex.org/work/W2167746394> ?p ?o ?g. }

Showing items 1 to 100 of ±122 with 100 items per page.

W2167746394 endingPage "23275" @default.
W2167746394 startingPage "23270" @default.
W2167746394 abstract "The D1 protein of the photosystem II reaction center is thought to be the most light-sensitive component of the photosynthetic machinery. To understand the mechanisms underlying the light sensitivity of D1, we performed in vitro random mutagenesis of the psbA gene that codes for D1, transformed the unicellular cyanobacterium Synechocystis sp. PCC 6803 with mutated psbA , and selected phototolerant transformants that did not bleach in high intensity light. A region ofpsbA2 coding for 178 amino acids of the carboxyl-terminal portion of the peptide was subjected to random mutagenesis by low fidelity polymerase chain reaction amplification or by hydroxylamine treatment. This region contains the binding sites for QB, D2 (through Fe), and P680. Eighteen phototolerant mutants with single and multiple amino acid substitutions were selected from a half million transformants exposed to white light at 320 μmol m−2s−1. A strain transformed with non-mutagenizedpsbA2 became bleached under the same conditions. Site-directed mutagenesis has confirmed that one or more substitutions of amino acids at residues 234, 254, 260, 267, 322, 326, and 328 confers phototolerance. The rate of degradation of D1 protein was not appreciably affected by the mutations. Reduced bleaching of mutant cyanobacterial cells may result from continued buildup of photosynthetic pigment systems caused by changes in redox signals originating from D1. The D1 protein of the photosystem II reaction center is thought to be the most light-sensitive component of the photosynthetic machinery. To understand the mechanisms underlying the light sensitivity of D1, we performed in vitro random mutagenesis of the psbA gene that codes for D1, transformed the unicellular cyanobacterium Synechocystis sp. PCC 6803 with mutated psbA , and selected phototolerant transformants that did not bleach in high intensity light. A region ofpsbA2 coding for 178 amino acids of the carboxyl-terminal portion of the peptide was subjected to random mutagenesis by low fidelity polymerase chain reaction amplification or by hydroxylamine treatment. This region contains the binding sites for QB, D2 (through Fe), and P680. Eighteen phototolerant mutants with single and multiple amino acid substitutions were selected from a half million transformants exposed to white light at 320 μmol m−2s−1. A strain transformed with non-mutagenizedpsbA2 became bleached under the same conditions. Site-directed mutagenesis has confirmed that one or more substitutions of amino acids at residues 234, 254, 260, 267, 322, 326, and 328 confers phototolerance. The rate of degradation of D1 protein was not appreciably affected by the mutations. Reduced bleaching of mutant cyanobacterial cells may result from continued buildup of photosynthetic pigment systems caused by changes in redox signals originating from D1. photosystem polymerase chain reaction Tris-HCl/EDTA Although photosynthetic organisms require light for growth, they can suffer damage from high light intensity, especially at low temperatures and reduced concentrations of CO2 (1Powles S.B. Annu. Rev. Plant Physiol. 1984; 35: 15-44Crossref Google Scholar). The loss of photosynthetic productivity that occurs when organisms are exposed to visible light quanta above the level required for saturating photosynthetic electron flow is known as “photoinhibition” (2Kyle D.J. Kyle D.J. Osmond C.B. Arntzen C.J. Photoinhibition. Elsevier Science Publishers B.V., Amsterdam1987: 197-226Google Scholar). Under photoinhibitory conditions, the reaction center of photosystem (PS)1 II, which consists of D1 and D2 proteins (3Nanba O. Satoh K. Proc. Natl. Acad. Sci. U. S. A. 1987; 84: 109-112Crossref PubMed Google Scholar), is specifically inactivated (4Prasil O. Adir N. Ohad I. Barber J. The Photosystems: Structure, Function and Molecular Biology. Elsevier Science Publishers B.V., Amsterdam1992: 295-348Crossref Google Scholar, 5Aro E.-M. Virgin I. Andersson B. Biochim. Biophys. Acta. 1993; 1143: 113-134Crossref PubMed Scopus (1892) Google Scholar). Although the precise mechanisms of photoinactivation have not been fully elucidated, the process involves several steps, including an initial reversible reduction of electron flow and irreversible damage to the D1 protein (6Mattoo A.K. Hoffman-Falk H. Marder J.B. Edelman M. Proc. Natl. Acad. Sci. U. S. A. 1984; 81: 1380-1384Crossref PubMed Google Scholar, 7Ohad I. Kyle D.J. Arntzen C.J. J. Cell Biol. 1984; 99: 481-485Crossref PubMed Scopus (364) Google Scholar, 8Mattoo A.K. Marder J.B. Edelman M. Cell. 1989; 56: 241-246Abstract Full Text PDF PubMed Scopus (250) Google Scholar). Recovery of PSII activity can occur when irreversibly photodamaged D1 is replaced by newly synthesized protein (7Ohad I. Kyle D.J. Arntzen C.J. J. Cell Biol. 1984; 99: 481-485Crossref PubMed Scopus (364) Google Scholar).Site-directed or deletion mutagenesis has been employed to investigate the basic mechanisms of the photosensitivity, including the relationships between the structure and function of D1 (9Mäenpää P. Kallio T. Mulo P. Salih G. Aro E.-M. Tyystjärvi E. Jansson C. Plant Mol. Biol. 1993; 22: 1-12Crossref PubMed Scopus (33) Google Scholar, 10Tyystjärvi T. Aro E.-M. Jansson C. Mäenpää P. Plant Mol. Biol. 1994; 25: 517-526Crossref PubMed Scopus (48) Google Scholar, 11Kless H. Oren-Shamir M. Malkin S. McIntosh L. Edelman M. Biochemistry. 1994; 33: 10501-10507Crossref PubMed Scopus (47) Google Scholar, 12Nixon P.J. Komenda J. Barber J. Deak Z. Vass I. Diner B.A. J. Biol. Chem. 1995; 270: 14919-14927Abstract Full Text Full Text PDF PubMed Scopus (61) Google Scholar). Although site-specific mutagenesis seldom confers new function, this technique has produced some mutants in which PSII and D1 gained partial resistance to high irradiance (9Mäenpää P. Kallio T. Mulo P. Salih G. Aro E.-M. Tyystjärvi E. Jansson C. Plant Mol. Biol. 1993; 22: 1-12Crossref PubMed Scopus (33) Google Scholar, 10Tyystjärvi T. Aro E.-M. Jansson C. Mäenpää P. Plant Mol. Biol. 1994; 25: 517-526Crossref PubMed Scopus (48) Google Scholar, 12Nixon P.J. Komenda J. Barber J. Deak Z. Vass I. Diner B.A. J. Biol. Chem. 1995; 270: 14919-14927Abstract Full Text Full Text PDF PubMed Scopus (61) Google Scholar). In vitro random mutagenesis, ideally saturation mutagenesis, coupled with appropriate methods for screening mutants, is a useful method to obtain new species of D1 protein that are phototolerant. For these experiments, we have chosen the unicellular cyanobacterium Synechocystis sp. PCC 6803. In addition to having plant-like photosynthetic activity,Synechocystis can be genetically transformed at high efficiency and can be easily screened as colonies under defined conditions (13Dzelzkalns V.A. Bogorad L. J. Bacteriol. 1986; 165: 964-971Crossref PubMed Google Scholar).DISCUSSIONWhat events occur prior to bleaching in cyanobacterial cells under irradiance? The cell-doubling times of the control strain KC and all mutants were nearly identical at approximately 24 h under irradiance at 500 μmol m−2 s−1 (data not shown), when the control strain gradually bleached. Therefore, bleaching is an event primarily independent of cell growth. Superoxide anion radical known as the primary product of oxygen photoreduction in thylakoids (27Asada K. Foyer C.H. Mullineaux P.M. Causes of Photooxidative Stress and Amelioration of Defense Systems in Plants. CRC Press, Boca Raton, FL1994: 77-104Google Scholar) may degrade photosynthetic pigments. Absorption spectra of the control strain KC and mutant G3 as determined time-sequentially after exposure to irradiance indicate that chlorophyll a content diminishes specifically during bleaching in the control strain (28Narusaka Y. Murakami A. Saeki M. Kobayashi H. Satoh K. Plant Sci. 1996; 115: 261-266Crossref Scopus (9) Google Scholar). This observation is contrary to the phenomenon ofsodB − mutant of the cyanobacteriumSynechococcus sp PCC 7942, which is deficient in functional iron superoxide dismutase (29Thomas D.J. Avenson T.J. Thomas J.B. Herbert S.K. Plant Physiol. 1998; 116: 1593-1602Crossref PubMed Scopus (67) Google Scholar), where the carotenoid-to-chlorophyll ratio strikingly decreased when cultured in the presence of methyl viologen. Active oxygen species have also been reported to degrade D1 protein (30Miyao M. Biochemistry. 1994; 33: 9722-9730Crossref PubMed Scopus (117) Google Scholar), in relation to “damage-repair cycle of D1 protein” (26Greenberg B.M. Gaba V. Mattoo A.K. Edelman M. EMBO J. 1987; 6: 2865-2869Crossref PubMed Scopus (218) Google Scholar, 31Samuelsson G. Lönneborg A. Rosenqvist E. Gustafsson P. Öquist G. Plant Physiol. 1985; 79: 992-995Crossref PubMed Google Scholar, 32Greer D.H. Berry J.A. Björkman O. Planta. 1986; 168: 253-260PubMed Google Scholar). In the present investigation, the rate of degradation of D1 protein did not change in the wild-type and mutant strains under irradiance (Fig. 4). Therefore, the possibility that generation of oxygen radicals is reduced in the mutants may be excluded.Phototolerance associated with PSII in photosynthetic organisms has been suggested to occur by one or more mechanisms: (i) an efficient energy dissipation or leakage at the stage of excitation energy transfer in the pigment system (33Weis E. Berry J.A. Biochim. Biophys. Acta. 1987; 894: 198-208Crossref Scopus (496) Google Scholar, 34Demmig-Adams B. Biochim. Biophys. Acta. 1990; 1020: 1-24Crossref Scopus (1377) Google Scholar, 35Krause G.H. Weis E. Annu. Rev. Plant Physiol. Plant Mol. Biol. 1991; 42: 313-349Crossref Scopus (3627) Google Scholar, 36Andersson B. Styring S. Lee C.P. Current Topics in Bioenergetics. Academic Press, San Diego1991: 2-81Google Scholar) capable of being detected by the fluorescence emission spectra at low temperatures (37Anderson J.M. Andersson B. Trends Biochem. Sci. 1988; 13: 351-355Abstract Full Text PDF PubMed Scopus (171) Google Scholar, 38Genty B. Briantais J.-M. Baker N.R. Biochim. Biophys. Acta. 1989; 990: 87-92Crossref Scopus (6865) Google Scholar, 39Rees D. Noctor G.D. Horton P. Fertilizer Res. 1990; 25: 199-211Google Scholar), and (ii) an efficient electron leakage via some kind of cyclic electron flow around the PSII in the electron transport system due to instability or redox potential change of the primary or secondary reactants as detected by shifts in thermoluminescence bands (40Thompson L.K. Brudvig G.W. Biochemistry. 1988; 27: 6653-6658Crossref PubMed Scopus (254) Google Scholar, 41Telfer A. Rivas J.D.L. Barber J. Biochim. Biophys. Acta. 1991; 1060: 106-114Crossref Scopus (136) Google Scholar). It is hypothesized that redox signaling can regulate gene expression (42Allen J.F. Alexciev K. Hakansson G. Curr. Biol. 1995; 5: 869-872Abstract Full Text Full Text PDF PubMed Scopus (81) Google Scholar, 43Allen J.F. Physiol. Plant. 1995; 93: 196-205Crossref Scopus (131) Google Scholar) and physical linkage that facilitates energy transfer between light-harvesting complex II and PSII/PSI (44Allen J.F. Nilsson A. Physiol. Plant. 1997; 100: 863-868Crossref Google Scholar, 45Vener A.V. VanKan P.J.M. Rich P.R. Ohad I. Andersson B. Proc. Natl. Acad. Sci. U. S. A. 1997; 94: 1585-1590Crossref PubMed Scopus (247) Google Scholar, 46Gal A. Zer H. Ohad I. Physiol. Plant. 1997; 100: 869-885Crossref Google Scholar) through protein phosphorylation. The redox sensor is postulated to be an electron carrier located between PSII and PSI (42Allen J.F. Alexciev K. Hakansson G. Curr. Biol. 1995; 5: 869-872Abstract Full Text Full Text PDF PubMed Scopus (81) Google Scholar), and a kinase is activated by a reduced cytochrome b/f complex interacting with a plastoquinol at the QB site (46Gal A. Zer H. Ohad I. Physiol. Plant. 1997; 100: 869-885Crossref Google Scholar).Our preliminary analysis of the thermoluminescence profiles indicates that changes by the mutagenesis of D1 in the equilibrium between QA and QB due to (i) changes in their stability including redox-potential and (ii) low efficiency of electron transport in PSII, could explain the observed phototolerance (47Minagawa J. Narusaka Y. Inoue Y. Satoh K. Biochemistry. 1999; 38: 770-775Crossref PubMed Scopus (35) Google Scholar). Analysis of the fluorescence measurements indicates that these mutants perform low quantum-yield electron flow in PSII (47Minagawa J. Narusaka Y. Inoue Y. Satoh K. Biochemistry. 1999; 38: 770-775Crossref PubMed Scopus (35) Google Scholar). Therefore, it is possible that mutated D1 proteins influence redox signaling and in this way interfere with down-regulation of the biogenesis of the photosynthetic apparatus. This may explain the retention of cell pigmentation in these mutants under high irradiance. These hypotheses in turn suggest the existence of an intrinsic protection mechanism in wild-type cells that copes with photoinhibition by down-regulating phycobilisome formation.In phototolerant mutant species of D1, most amino acid conversions involved changes from nonpolar species to polar or charged ones,i.e. to Ser (32%), Asp (14%), Arg (7%), and Tyr (5%); the conversion of Phe to Ser occurred most often. This may indicate the increase in the hydrophilic or hydrogen-bonding interactions in the D1 protein is responsible for the enhanced phototolerance of the organism. Interestingly, Ser → Phe substitution in the lumenal loop of the D2 protein (48Ermakova-Gerdes S. Shestakov S. Vermaas W. Plant Mol. Biol. 1996; 30: 243-254Crossref PubMed Scopus (20) Google Scholar) appears to endow PSII with photosensitivity. Further biophysical analysis of cyanobacterial cells harboring the mutated species of D1 is needed to prove this proposal. Although photosynthetic organisms require light for growth, they can suffer damage from high light intensity, especially at low temperatures and reduced concentrations of CO2 (1Powles S.B. Annu. Rev. Plant Physiol. 1984; 35: 15-44Crossref Google Scholar). The loss of photosynthetic productivity that occurs when organisms are exposed to visible light quanta above the level required for saturating photosynthetic electron flow is known as “photoinhibition” (2Kyle D.J. Kyle D.J. Osmond C.B. Arntzen C.J. Photoinhibition. Elsevier Science Publishers B.V., Amsterdam1987: 197-226Google Scholar). Under photoinhibitory conditions, the reaction center of photosystem (PS)1 II, which consists of D1 and D2 proteins (3Nanba O. Satoh K. Proc. Natl. Acad. Sci. U. S. A. 1987; 84: 109-112Crossref PubMed Google Scholar), is specifically inactivated (4Prasil O. Adir N. Ohad I. Barber J. The Photosystems: Structure, Function and Molecular Biology. Elsevier Science Publishers B.V., Amsterdam1992: 295-348Crossref Google Scholar, 5Aro E.-M. Virgin I. Andersson B. Biochim. Biophys. Acta. 1993; 1143: 113-134Crossref PubMed Scopus (1892) Google Scholar). Although the precise mechanisms of photoinactivation have not been fully elucidated, the process involves several steps, including an initial reversible reduction of electron flow and irreversible damage to the D1 protein (6Mattoo A.K. Hoffman-Falk H. Marder J.B. Edelman M. Proc. Natl. Acad. Sci. U. S. A. 1984; 81: 1380-1384Crossref PubMed Google Scholar, 7Ohad I. Kyle D.J. Arntzen C.J. J. Cell Biol. 1984; 99: 481-485Crossref PubMed Scopus (364) Google Scholar, 8Mattoo A.K. Marder J.B. Edelman M. Cell. 1989; 56: 241-246Abstract Full Text PDF PubMed Scopus (250) Google Scholar). Recovery of PSII activity can occur when irreversibly photodamaged D1 is replaced by newly synthesized protein (7Ohad I. Kyle D.J. Arntzen C.J. J. Cell Biol. 1984; 99: 481-485Crossref PubMed Scopus (364) Google Scholar). Site-directed or deletion mutagenesis has been employed to investigate the basic mechanisms of the photosensitivity, including the relationships between the structure and function of D1 (9Mäenpää P. Kallio T. Mulo P. Salih G. Aro E.-M. Tyystjärvi E. Jansson C. Plant Mol. Biol. 1993; 22: 1-12Crossref PubMed Scopus (33) Google Scholar, 10Tyystjärvi T. Aro E.-M. Jansson C. Mäenpää P. Plant Mol. Biol. 1994; 25: 517-526Crossref PubMed Scopus (48) Google Scholar, 11Kless H. Oren-Shamir M. Malkin S. McIntosh L. Edelman M. Biochemistry. 1994; 33: 10501-10507Crossref PubMed Scopus (47) Google Scholar, 12Nixon P.J. Komenda J. Barber J. Deak Z. Vass I. Diner B.A. J. Biol. Chem. 1995; 270: 14919-14927Abstract Full Text Full Text PDF PubMed Scopus (61) Google Scholar). Although site-specific mutagenesis seldom confers new function, this technique has produced some mutants in which PSII and D1 gained partial resistance to high irradiance (9Mäenpää P. Kallio T. Mulo P. Salih G. Aro E.-M. Tyystjärvi E. Jansson C. Plant Mol. Biol. 1993; 22: 1-12Crossref PubMed Scopus (33) Google Scholar, 10Tyystjärvi T. Aro E.-M. Jansson C. Mäenpää P. Plant Mol. Biol. 1994; 25: 517-526Crossref PubMed Scopus (48) Google Scholar, 12Nixon P.J. Komenda J. Barber J. Deak Z. Vass I. Diner B.A. J. Biol. Chem. 1995; 270: 14919-14927Abstract Full Text Full Text PDF PubMed Scopus (61) Google Scholar). In vitro random mutagenesis, ideally saturation mutagenesis, coupled with appropriate methods for screening mutants, is a useful method to obtain new species of D1 protein that are phototolerant. For these experiments, we have chosen the unicellular cyanobacterium Synechocystis sp. PCC 6803. In addition to having plant-like photosynthetic activity,Synechocystis can be genetically transformed at high efficiency and can be easily screened as colonies under defined conditions (13Dzelzkalns V.A. Bogorad L. J. Bacteriol. 1986; 165: 964-971Crossref PubMed Google Scholar). DISCUSSIONWhat events occur prior to bleaching in cyanobacterial cells under irradiance? The cell-doubling times of the control strain KC and all mutants were nearly identical at approximately 24 h under irradiance at 500 μmol m−2 s−1 (data not shown), when the control strain gradually bleached. Therefore, bleaching is an event primarily independent of cell growth. Superoxide anion radical known as the primary product of oxygen photoreduction in thylakoids (27Asada K. Foyer C.H. Mullineaux P.M. Causes of Photooxidative Stress and Amelioration of Defense Systems in Plants. CRC Press, Boca Raton, FL1994: 77-104Google Scholar) may degrade photosynthetic pigments. Absorption spectra of the control strain KC and mutant G3 as determined time-sequentially after exposure to irradiance indicate that chlorophyll a content diminishes specifically during bleaching in the control strain (28Narusaka Y. Murakami A. Saeki M. Kobayashi H. Satoh K. Plant Sci. 1996; 115: 261-266Crossref Scopus (9) Google Scholar). This observation is contrary to the phenomenon ofsodB − mutant of the cyanobacteriumSynechococcus sp PCC 7942, which is deficient in functional iron superoxide dismutase (29Thomas D.J. Avenson T.J. Thomas J.B. Herbert S.K. Plant Physiol. 1998; 116: 1593-1602Crossref PubMed Scopus (67) Google Scholar), where the carotenoid-to-chlorophyll ratio strikingly decreased when cultured in the presence of methyl viologen. Active oxygen species have also been reported to degrade D1 protein (30Miyao M. Biochemistry. 1994; 33: 9722-9730Crossref PubMed Scopus (117) Google Scholar), in relation to “damage-repair cycle of D1 protein” (26Greenberg B.M. Gaba V. Mattoo A.K. Edelman M. EMBO J. 1987; 6: 2865-2869Crossref PubMed Scopus (218) Google Scholar, 31Samuelsson G. Lönneborg A. Rosenqvist E. Gustafsson P. Öquist G. Plant Physiol. 1985; 79: 992-995Crossref PubMed Google Scholar, 32Greer D.H. Berry J.A. Björkman O. Planta. 1986; 168: 253-260PubMed Google Scholar). In the present investigation, the rate of degradation of D1 protein did not change in the wild-type and mutant strains under irradiance (Fig. 4). Therefore, the possibility that generation of oxygen radicals is reduced in the mutants may be excluded.Phototolerance associated with PSII in photosynthetic organisms has been suggested to occur by one or more mechanisms: (i) an efficient energy dissipation or leakage at the stage of excitation energy transfer in the pigment system (33Weis E. Berry J.A. Biochim. Biophys. Acta. 1987; 894: 198-208Crossref Scopus (496) Google Scholar, 34Demmig-Adams B. Biochim. Biophys. Acta. 1990; 1020: 1-24Crossref Scopus (1377) Google Scholar, 35Krause G.H. Weis E. Annu. Rev. Plant Physiol. Plant Mol. Biol. 1991; 42: 313-349Crossref Scopus (3627) Google Scholar, 36Andersson B. Styring S. Lee C.P. Current Topics in Bioenergetics. Academic Press, San Diego1991: 2-81Google Scholar) capable of being detected by the fluorescence emission spectra at low temperatures (37Anderson J.M. Andersson B. Trends Biochem. Sci. 1988; 13: 351-355Abstract Full Text PDF PubMed Scopus (171) Google Scholar, 38Genty B. Briantais J.-M. Baker N.R. Biochim. Biophys. Acta. 1989; 990: 87-92Crossref Scopus (6865) Google Scholar, 39Rees D. Noctor G.D. Horton P. Fertilizer Res. 1990; 25: 199-211Google Scholar), and (ii) an efficient electron leakage via some kind of cyclic electron flow around the PSII in the electron transport system due to instability or redox potential change of the primary or secondary reactants as detected by shifts in thermoluminescence bands (40Thompson L.K. Brudvig G.W. Biochemistry. 1988; 27: 6653-6658Crossref PubMed Scopus (254) Google Scholar, 41Telfer A. Rivas J.D.L. Barber J. Biochim. Biophys. Acta. 1991; 1060: 106-114Crossref Scopus (136) Google Scholar). It is hypothesized that redox signaling can regulate gene expression (42Allen J.F. Alexciev K. Hakansson G. Curr. Biol. 1995; 5: 869-872Abstract Full Text Full Text PDF PubMed Scopus (81) Google Scholar, 43Allen J.F. Physiol. Plant. 1995; 93: 196-205Crossref Scopus (131) Google Scholar) and physical linkage that facilitates energy transfer between light-harvesting complex II and PSII/PSI (44Allen J.F. Nilsson A. Physiol. Plant. 1997; 100: 863-868Crossref Google Scholar, 45Vener A.V. VanKan P.J.M. Rich P.R. Ohad I. Andersson B. Proc. Natl. Acad. Sci. U. S. A. 1997; 94: 1585-1590Crossref PubMed Scopus (247) Google Scholar, 46Gal A. Zer H. Ohad I. Physiol. Plant. 1997; 100: 869-885Crossref Google Scholar) through protein phosphorylation. The redox sensor is postulated to be an electron carrier located between PSII and PSI (42Allen J.F. Alexciev K. Hakansson G. Curr. Biol. 1995; 5: 869-872Abstract Full Text Full Text PDF PubMed Scopus (81) Google Scholar), and a kinase is activated by a reduced cytochrome b/f complex interacting with a plastoquinol at the QB site (46Gal A. Zer H. Ohad I. Physiol. Plant. 1997; 100: 869-885Crossref Google Scholar).Our preliminary analysis of the thermoluminescence profiles indicates that changes by the mutagenesis of D1 in the equilibrium between QA and QB due to (i) changes in their stability including redox-potential and (ii) low efficiency of electron transport in PSII, could explain the observed phototolerance (47Minagawa J. Narusaka Y. Inoue Y. Satoh K. Biochemistry. 1999; 38: 770-775Crossref PubMed Scopus (35) Google Scholar). Analysis of the fluorescence measurements indicates that these mutants perform low quantum-yield electron flow in PSII (47Minagawa J. Narusaka Y. Inoue Y. Satoh K. Biochemistry. 1999; 38: 770-775Crossref PubMed Scopus (35) Google Scholar). Therefore, it is possible that mutated D1 proteins influence redox signaling and in this way interfere with down-regulation of the biogenesis of the photosynthetic apparatus. This may explain the retention of cell pigmentation in these mutants under high irradiance. These hypotheses in turn suggest the existence of an intrinsic protection mechanism in wild-type cells that copes with photoinhibition by down-regulating phycobilisome formation.In phototolerant mutant species of D1, most amino acid conversions involved changes from nonpolar species to polar or charged ones,i.e. to Ser (32%), Asp (14%), Arg (7%), and Tyr (5%); the conversion of Phe to Ser occurred most often. This may indicate the increase in the hydrophilic or hydrogen-bonding interactions in the D1 protein is responsible for the enhanced phototolerance of the organism. Interestingly, Ser → Phe substitution in the lumenal loop of the D2 protein (48Ermakova-Gerdes S. Shestakov S. Vermaas W. Plant Mol. Biol. 1996; 30: 243-254Crossref PubMed Scopus (20) Google Scholar) appears to endow PSII with photosensitivity. Further biophysical analysis of cyanobacterial cells harboring the mutated species of D1 is needed to prove this proposal. What events occur prior to bleaching in cyanobacterial cells under irradiance? The cell-doubling times of the control strain KC and all mutants were nearly identical at approximately 24 h under irradiance at 500 μmol m−2 s−1 (data not shown), when the control strain gradually bleached. Therefore, bleaching is an event primarily independent of cell growth. Superoxide anion radical known as the primary product of oxygen photoreduction in thylakoids (27Asada K. Foyer C.H. Mullineaux P.M. Causes of Photooxidative Stress and Amelioration of Defense Systems in Plants. CRC Press, Boca Raton, FL1994: 77-104Google Scholar) may degrade photosynthetic pigments. Absorption spectra of the control strain KC and mutant G3 as determined time-sequentially after exposure to irradiance indicate that chlorophyll a content diminishes specifically during bleaching in the control strain (28Narusaka Y. Murakami A. Saeki M. Kobayashi H. Satoh K. Plant Sci. 1996; 115: 261-266Crossref Scopus (9) Google Scholar). This observation is contrary to the phenomenon ofsodB − mutant of the cyanobacteriumSynechococcus sp PCC 7942, which is deficient in functional iron superoxide dismutase (29Thomas D.J. Avenson T.J. Thomas J.B. Herbert S.K. Plant Physiol. 1998; 116: 1593-1602Crossref PubMed Scopus (67) Google Scholar), where the carotenoid-to-chlorophyll ratio strikingly decreased when cultured in the presence of methyl viologen. Active oxygen species have also been reported to degrade D1 protein (30Miyao M. Biochemistry. 1994; 33: 9722-9730Crossref PubMed Scopus (117) Google Scholar), in relation to “damage-repair cycle of D1 protein” (26Greenberg B.M. Gaba V. Mattoo A.K. Edelman M. EMBO J. 1987; 6: 2865-2869Crossref PubMed Scopus (218) Google Scholar, 31Samuelsson G. Lönneborg A. Rosenqvist E. Gustafsson P. Öquist G. Plant Physiol. 1985; 79: 992-995Crossref PubMed Google Scholar, 32Greer D.H. Berry J.A. Björkman O. Planta. 1986; 168: 253-260PubMed Google Scholar). In the present investigation, the rate of degradation of D1 protein did not change in the wild-type and mutant strains under irradiance (Fig. 4). Therefore, the possibility that generation of oxygen radicals is reduced in the mutants may be excluded. Phototolerance associated with PSII in photosynthetic organisms has been suggested to occur by one or more mechanisms: (i) an efficient energy dissipation or leakage at the stage of excitation energy transfer in the pigment system (33Weis E. Berry J.A. Biochim. Biophys. Acta. 1987; 894: 198-208Crossref Scopus (496) Google Scholar, 34Demmig-Adams B. Biochim. Biophys. Acta. 1990; 1020: 1-24Crossref Scopus (1377) Google Scholar, 35Krause G.H. Weis E. Annu. Rev. Plant Physiol. Plant Mol. Biol. 1991; 42: 313-349Crossref Scopus (3627) Google Scholar, 36Andersson B. Styring S. Lee C.P. Current Topics in Bioenergetics. Academic Press, San Diego1991: 2-81Google Scholar) capable of being detected by the fluorescence emission spectra at low temperatures (37Anderson J.M. Andersson B. Trends Biochem. Sci. 1988; 13: 351-355Abstract Full Text PDF PubMed Scopus (171) Google Scholar, 38Genty B. Briantais J.-M. Baker N.R. Biochim. Biophys. Acta. 1989; 990: 87-92Crossref Scopus (6865) Google Scholar, 39Rees D. Noctor G.D. Horton P. Fertilizer Res. 1990; 25: 199-211Google Scholar), and (ii) an efficient electron leakage via some kind of cyclic electron flow around the PSII in the electron transport system due to instability or redox potential change of the primary or secondary reactants as detected by shifts in thermoluminescence bands (40Thompson L.K. Brudvig G.W. Biochemistry. 1988; 27: 6653-6658Crossref PubMed Scopus (254) Google Scholar, 41Telfer A. Rivas J.D.L. Barber J. Biochim. Biophys. Acta. 1991; 1060: 106-114Crossref Scopus (136) Google Scholar). It is hypothesized that redox signaling can regulate gene expression (42Allen J.F. Alexciev K. Hakansson G. Curr. Biol. 1995; 5: 869-872Abstract Full Text Full Text PDF PubMed Scopus (81) Google Scholar, 43Allen J.F. Physiol. Plant. 1995; 93: 196-205Crossref Scopus (131) Google Scholar) and physical linkage that facilitates energy transfer between light-harvesting complex II and PSII/PSI (44Allen J.F. Nilsson A. Physiol. Plant. 1997; 100: 863-868Crossref Google Scholar, 45Vener A.V. VanKan P.J.M. Rich P.R. Ohad I. Andersson B. Proc. Natl. Acad. Sci. U. S. A. 1997; 94: 1585-1590Crossref PubMed Scopus (247) Google Scholar, 46Gal A. Zer H. Ohad I. Physiol. Plant. 1997; 100: 869-885Crossref Google Scholar) through protein phosphorylation. The redox sensor is postulated to be an electron carrier located between PSII and PSI (42Allen J.F. Alexciev K. Hakansson G. Curr. Biol. 1995; 5: 869-872Abstract Full Text Full Text PDF PubMed Scopus (81) Google Scholar), and a kinase is activated by a reduced cytochrome b/f complex interacting with a plastoquinol at the QB site (46Gal A. Zer H. Ohad I. Physiol. Plant. 1997; 100: 869-885Crossref Google Scholar). Our preliminary analysis of the thermoluminescence profiles indicates that changes by the mutagenesis of D1 in the equilibrium between QA and QB due to (i) changes in their stability including redox-potential and (ii) low efficiency of electron transport in PSII, could explain the observed phototolerance (47Minagawa J. Narusaka Y. Inoue Y. Satoh K. Biochemistry. 1999; 38: 770-775Crossref PubMed Scopus (35) Google Scholar). Analysis of the fluorescence measurements indicates that these mutants perform low quantum-yield electron flow in PSII (47Minagawa J. Narusaka Y. Inoue Y. Satoh K. Biochemistry. 1999; 38: 770-775Crossref PubMed Scopus (35) Google Scholar). Therefore, it is possible that mutated D1 proteins influence redox signaling and in this way interfere with down-regulation of the biogenesis of the photosynthetic apparatus. This may explain the retention of cell pigmentation in these mutants under high irradiance. These hypotheses in turn suggest the existence of an intrinsic protection mechanism in wild-type cells that copes with photoinhibition by down-regulating phycobilisome formation. In phototolerant mutant species of D1, most amino acid conversions involved changes from nonpolar species to polar or charged ones,i.e. to Ser (32%), Asp (14%), Arg (7%), and Tyr (5%); the conversion of Phe to Ser occurred most often. This may indicate the increase in the hydrophilic or hydrogen-bonding interactions in the D1 protein is responsible for the enhanced phototolerance of the organism. Interestingly, Ser → Phe substitution in the lumenal loop of the D2 protein (48Ermakova-Gerdes S. Shestakov S. Vermaas W. Plant Mol. Biol. 1996; 30: 243-254Crossref PubMed Scopus (20) Google Scholar) appears to endow PSII with photosensitivity. Further biophysical analysis of cyanobacterial cells harboring the mutated species of D1 is needed to prove this proposal. We thank R. J. Debus for providingSynechocystis sp. PCC 6803 strain Cm4Δ-1 and M. Ishiura and S. Aoki for the psbA2 gene. We are also indebted to Y. Yamamoto for identification of D1 protein by immunoprecipitation, N. Murata and T. Ogawa for gifts of Synechocystis sp. PCC 6803 wild-type strain and its genomic clones, and N. Shimoda and Y. Niwa for guidance of hydroxylamine for mutagenesis." @default.
W2167746394 created "2016-06-24" @default.
W2167746394 creator A5003899723 @default.
W2167746394 creator A5005766056 @default.
W2167746394 creator A5022236812 @default.
W2167746394 creator A5069043493 @default.
W2167746394 date "1999-08-01" @default.
W2167746394 modified "2023-09-28" @default.
W2167746394 title "In Vitro Random Mutagenesis of the D1 Protein of the Photosystem II Reaction Center Confers Phototolerance on the Cyanobacterium Synechocystis sp. PCC 6803" @default.
W2167746394 cites W1938201069 @default.
W2167746394 cites W1964900840 @default.
W2167746394 cites W1965653878 @default.
W2167746394 cites W1966356868 @default.
W2167746394 cites W1966772263 @default.
W2167746394 cites W1975892234 @default.
W2167746394 cites W1981443609 @default.
W2167746394 cites W1989585864 @default.
W2167746394 cites W1996363310 @default.
W2167746394 cites W2000872740 @default.
W2167746394 cites W2002688220 @default.
W2167746394 cites W2008468314 @default.
W2167746394 cites W2010601153 @default.
W2167746394 cites W2012060327 @default.
W2167746394 cites W2022433699 @default.
W2167746394 cites W2023185871 @default.
W2167746394 cites W2040829829 @default.
W2167746394 cites W2041498840 @default.
W2167746394 cites W2041907482 @default.
W2167746394 cites W2046049921 @default.
W2167746394 cites W2053194743 @default.
W2167746394 cites W2053657459 @default.
W2167746394 cites W2055322801 @default.
W2167746394 cites W2067741165 @default.
W2167746394 cites W2075552521 @default.
W2167746394 cites W2081939104 @default.
W2167746394 cites W2092947620 @default.
W2167746394 cites W2093861840 @default.
W2167746394 cites W2100488588 @default.
W2167746394 cites W2100837269 @default.
W2167746394 cites W2102643689 @default.
W2167746394 cites W2115492173 @default.
W2167746394 cites W2115663229 @default.
W2167746394 cites W2120060779 @default.
W2167746394 cites W2135370264 @default.
W2167746394 cites W2147426605 @default.
W2167746394 cites W2164834021 @default.
W2167746394 cites W2339677340 @default.
W2167746394 cites W2412802087 @default.
W2167746394 cites W349879792 @default.
W2167746394 doi "https://doi.org/10.1074/jbc.274.33.23270" @default.
W2167746394 hasPubMedId "https://pubmed.ncbi.nlm.nih.gov/10438502" @default.
W2167746394 hasPublicationYear "1999" @default.
W2167746394 type Work @default.
W2167746394 sameAs 2167746394 @default.
W2167746394 citedByCount "12" @default.
W2167746394 countsByYear W21677463942012 @default.
W2167746394 countsByYear W21677463942015 @default.
W2167746394 countsByYear W21677463942018 @default.
W2167746394 countsByYear W21677463942020 @default.
W2167746394 countsByYear W21677463942021 @default.
W2167746394 countsByYear W21677463942022 @default.
W2167746394 crossrefType "journal-article" @default.
W2167746394 hasAuthorship W2167746394A5003899723 @default.
W2167746394 hasAuthorship W2167746394A5005766056 @default.
W2167746394 hasAuthorship W2167746394A5022236812 @default.
W2167746394 hasAuthorship W2167746394A5069043493 @default.
W2167746394 hasBestOaLocation W21677463941 @default.
W2167746394 hasConcept C104317684 @default.
W2167746394 hasConcept C143065580 @default.
W2167746394 hasConcept C16318435 @default.
W2167746394 hasConcept C183688256 @default.
W2167746394 hasConcept C185592680 @default.
W2167746394 hasConcept C188231169 @default.
W2167746394 hasConcept C202751555 @default.
W2167746394 hasConcept C2779463800 @default.
W2167746394 hasConcept C2779669040 @default.
W2167746394 hasConcept C2780238584 @default.
W2167746394 hasConcept C501734568 @default.
W2167746394 hasConcept C523546767 @default.
W2167746394 hasConcept C54355233 @default.
W2167746394 hasConcept C55493867 @default.
W2167746394 hasConcept C8010536 @default.
W2167746394 hasConcept C80298142 @default.
W2167746394 hasConcept C86803240 @default.
W2167746394 hasConceptScore W2167746394C104317684 @default.
W2167746394 hasConceptScore W2167746394C143065580 @default.
W2167746394 hasConceptScore W2167746394C16318435 @default.
W2167746394 hasConceptScore W2167746394C183688256 @default.
W2167746394 hasConceptScore W2167746394C185592680 @default.
W2167746394 hasConceptScore W2167746394C188231169 @default.
W2167746394 hasConceptScore W2167746394C202751555 @default.
W2167746394 hasConceptScore W2167746394C2779463800 @default.
W2167746394 hasConceptScore W2167746394C2779669040 @default.
W2167746394 hasConceptScore W2167746394C2780238584 @default.
W2167746394 hasConceptScore W2167746394C501734568 @default.
W2167746394 hasConceptScore W2167746394C523546767 @default.
W2167746394 hasConceptScore W2167746394C54355233 @default.
W2167746394 hasConceptScore W2167746394C55493867 @default.