FRINK Linked Data Fragments server

Matches in SemOpenAlex for { <https://semopenalex.org/work/W13223381> ?p ?o ?g. }

• W13223381 abstract "The low-density lipoprotein receptor (LDL-R) is a cell surface receptor, which functions to maintain cholesterol homeostasis by endocytosis of apolipoprotein (apo)E-and apoB-100-containing lipoproteins in the liver. Many genetic defects associated with this receptor have been characterized, which result in accumulation of LDL particles in the blood stream and development of familial hypercholesterolemia. LDL-R belongs to the LDL receptor superfamily, which is composed of similar mosaic-gene cell surface receptors, such as the very low-density lipoprotein, apoE, vitellogenin and megalin receptors. LDL-R is composed of five distinct domains, namely ligand-binding (LB), epidermal growth factor (EGF)-precursor homology, 0-linked sugar, transmembrane and cytoplasmic domains.          The aim of this project was to analyze the structures of segments of the human LDL-R using nuclear magnetic resonance (NMR) spectroscopy. The segments studied were the concatemer of the first and second ligand-binding domain (LB1-2), the first EGF module (EGFA), a concatemer of the first and second EGF modules (EGFA-B), and a concatemer of the last LB and the first EGF modules (LB7-EGFA).           The LB domain consists of seven modules of ~40 residues which are interconnected by short (4 or 12-residue) linkers. The LB module is rich in acidic residues, including four conserved acidic residues that are involved in ligating a calcium ion, and is stabilized by three disulfide bonds with a Cys(I=III), Cys(II-V) and Cys(IV-VI) pattern. LB1-2 was chosen in this study to model the behavior of the modules of the LB domain. NMR studies revealed that the linker residues, which were defined by residues between the last cysteine of the first module and the first cysteine of the second module (L64-S65-V66-T67), were mobile. The Hα and NH resonances of the linker residues were located in the random coil region of the NMR spectra, and no NOE Interaction was detected between the individual modules. The calculated structures show that the secondary structures of LB1 and LB2 are composed of a short β-hairpin, followed by two small 3-10 helices. The C-terminal 3-10 helix contains the conserved SDE sequence, and is a part of the calcium binding site. The LB module has a small core, composed of a hydrophobic cluster formed by the conserved Phe and IIe residues and a calcium binding site. The structures of the modules In the LB1-2 concatemer are similar to those of the individual modules, indicating that the structures of these LB modules are not altered upon concatenation. The flexibility of the linker of the LB domain of LDL-R could be important for precise LB module arrangements required to bind apoB and apoE ligands.         The epidermal growth factor (EGF)-precursor homology domain consists of three EGF modules (EGFA, B and C) and a YWTD-rich module. The EGF-precursor homology domain is thought to undergo conformational changes in the endosomes, which results in LDL-R-ligand dissociation. EGFA and EGFB both contain 41 residues and EGFC contains 56 residues. Each is stabilized by three disulfide bonds with Cys(I-III), Cys(II-IV) and Cys(V-VI) connectivity. The EGFA module has an incomplete EGF calcium binding consensus sequence (G314-T315-N316-E317) at the N-terminus. EGFA was studied first, to provide a reference for solving the structure of concatemers EGFA-B and LB7-EGFA.        EGFA has a short N-terminal 3-10 helix and a β-hairpin in the center. A comparison of EGFA NMR spectra acquired in the presence or absence of calcium ions at pH 5.5 was performed to model the module structural changes in the endosomal environment. In this acidic, calcium-free environment, EGFA exhibited structural changes near the calcium binding sites i.e. at the N-terminal region and at the turn of the P-hairpin. The disappearance of several NOE (nuclear Overhauser effect) cross peaks suggested increased structural mobility in these regions. These isolated structural changes, however, contrast with that observed in the LB modules, where calcium removal causes global collapse of the three-dimensional structure. EGFA-B consists of 82 residues, with two N-terminal calcium binding consensus sequences in each module (EGFA:G314-T315-N316-E317 and EGFB:D354-I355-D356-E357). EGFA and EGFB have similar backbone folds, with four β-hairpin secondary structures. EGFA-B adopts a rigid, rod-like structure, in which the module arrangements are restrained by the EGFB calcium binding site and the intermodule hydrophobic contacts between EGFA (F344 aromatic group) with the turn of β-hairpin 3 (EGFB E372 P-protons and G373-G373 backbones). The model-free analyses of 15N NMR relaxation data showed that the intermodule linker of EGFB is inflexible, with the model-free general order parameter > 0.8, as the results of participation in calcium binding. EGFA calcium binding site residues are more mobile compared to those of EGFB, reflecting a lower calcium binding affinity of the former. These observations contrast the characteristics of LB and EGF modules in terms of the flexibility of the intermodule linker and the role of calcium in maintaining structural integrity.             LB7-EGFA was analyzed to gain insight to the LB-EGF domain interface. This study was initiated by the modeling of LB7 structure, using the LB5 crystal structure as a template, to speed up the assignment process. Comparison of LB7 and EGFA Hα chemical shifts from the individual modules and from the concatemer showed small differences (< 0.2 ppm) near the central region of LB7 (D293-K294-V295-C296), and near the loop of EGFA major β-hairpin (I334-G335-Y336). From these two regions, intermodule NOEs were detected between the side chains of V295-K333; V295-I334 and backbone C296 HN-1334 H61. This intermodule Interactions, however, were weak and located in a small area, such that the orientation of the two modules could not be well constrained. {1H}-15N NOE measurements showed that a part of LB7-EGFA linker (T315- E317) appeared rigid as the result of their involvement as calcium ion ligands (NOE 0.86 ± 0.08). On the other hand, the LB7 residues C-terminal to the SDE calcium binding sequence exhibited some internal motions (NOE 0.69 ± 0.11). The flexibility of LB7-EGFA concatemer could be originated from this LB7 C-terminal region and the first residue of EGFA (G314). The substitution of G314 for the conserved EGF calcium binding N-terminal acidic residue most likely results in the elimination of backbone stabilization through calcium binding. This study shows that the LB domain is weakly coupled to its C-terminal EGF precursor homology domain, such that structural rearrangement that occurs in the LB domain during ligand binding may not greatly influence the structure of the rest of the receptor. This weak interaction between LB7-EGFA may be abolished when the pH and calcium ion concentration is low, which could be a mechanism for the receptor-ligand release in the endosome.           Having determined the structures of several LDL-R LB and EGF modules, FH mutations can now be classified into at least three groups. (1) Mutation of cysteine residues may result in misfolded structures. The LB and EGF modules have only diminutive cores, therefore they lack extensive hydrophobic packing or Ionic interactions commonly required to stabilize globular structures. (2) Mutation of calcium binding residues may cause the collapse of the 3D structure of LB modules, and in EGFA-B failure to maintain the rigid, linear structure. (3) Mutations of residues that are involved in module-module interactions, for example substitutions of the glycine residues at the turn of EGFB β-hairpin, would disrupt intermodule packing.          In summary, we have determined the three dimensional structures of several LDL-R concatemers. This structural data is important as the basis for the understanding of many diverse mosaic proteins and receptors belonging to the LDL-R gene superfamily." @default.
• W13223381 created "2016-06-24" @default.
• W13223381 creator A5027648157 @default.
• W13223381 date "2002-01-01" @default.
• W13223381 modified "2023-09-23" @default.
• W13223381 title "Dissection of the human low-density lipoprotein receptor structure using NMR spectroscopy" @default.
• W13223381 hasPublicationYear "2002" @default.
• W13223381 type Work @default.
• W13223381 sameAs 13223381 @default.
• W13223381 citedByCount "0" @default.
• W13223381 crossrefType "journal-article" @default.
• W13223381 hasAuthorship W13223381A5027648157 @default.
• W13223381 hasConcept C121332964 @default.
• W13223381 hasConcept C12554922 @default.
• W13223381 hasConcept C185592680 @default.
• W13223381 hasConcept C32891209 @default.
• W13223381 hasConcept C46141821 @default.
• W13223381 hasConcept C62520636 @default.
• W13223381 hasConcept C66974803 @default.
• W13223381 hasConcept C71240020 @default.
• W13223381 hasConcept C8010536 @default.
• W13223381 hasConcept C86803240 @default.
• W13223381 hasConceptScore W13223381C121332964 @default.
• W13223381 hasConceptScore W13223381C12554922 @default.
• W13223381 hasConceptScore W13223381C185592680 @default.
• W13223381 hasConceptScore W13223381C32891209 @default.
• W13223381 hasConceptScore W13223381C46141821 @default.
• W13223381 hasConceptScore W13223381C62520636 @default.
• W13223381 hasConceptScore W13223381C66974803 @default.
• W13223381 hasConceptScore W13223381C71240020 @default.
• W13223381 hasConceptScore W13223381C8010536 @default.
• W13223381 hasConceptScore W13223381C86803240 @default.
• W13223381 hasLocation W132233811 @default.
• W13223381 hasOpenAccess W13223381 @default.
• W13223381 hasPrimaryLocation W132233811 @default.
• W13223381 hasRelatedWork W1544744127 @default.
• W13223381 hasRelatedWork W186158443 @default.
• W13223381 hasRelatedWork W1965481756 @default.
• W13223381 hasRelatedWork W1969731710 @default.
• W13223381 hasRelatedWork W1976112293 @default.
• W13223381 hasRelatedWork W1979968104 @default.
• W13223381 hasRelatedWork W1984724591 @default.
• W13223381 hasRelatedWork W1990486414 @default.
• W13223381 hasRelatedWork W2018891862 @default.
• W13223381 hasRelatedWork W2035437208 @default.
• W13223381 hasRelatedWork W2049848125 @default.
• W13223381 hasRelatedWork W2053929376 @default.
• W13223381 hasRelatedWork W2071090580 @default.
• W13223381 hasRelatedWork W2072747162 @default.
• W13223381 hasRelatedWork W2079299597 @default.
• W13223381 hasRelatedWork W2135763899 @default.
• W13223381 hasRelatedWork W2143465412 @default.
• W13223381 hasRelatedWork W2158796888 @default.
• W13223381 hasRelatedWork W2163810400 @default.
• W13223381 hasRelatedWork W2024474839 @default.
• W13223381 isParatext "false" @default.
• W13223381 isRetracted "false" @default.
• W13223381 magId "13223381" @default.
• W13223381 workType "article" @default.