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• W2143157762 abstract "Article1 February 2007free access Structural basis of T-cell specificity and activation by the bacterial superantigen TSST-1 Beenu Moza Beenu Moza Boston Biomedical Research Institute, Watertown, MA, USA Search for more papers by this author Ashok K Varma Ashok K Varma Boston Biomedical Research Institute, Watertown, MA, USA Search for more papers by this author Rebecca A Buonpane Rebecca A Buonpane Department of Biochemistry, University of Illinois, Urbana, IL, USA Search for more papers by this author Penny Zhu Penny Zhu Boston Biomedical Research Institute, Watertown, MA, USA Search for more papers by this author Christine A Herfst Christine A Herfst Department of Microbiology and Immunology, Lawson Health Research Institute, University of Western Ontario, London, Ontario, Canada Search for more papers by this author Melissa J Nicholson Melissa J Nicholson Department of Cancer Immunology and AIDS, Dana Farber Cancer Research Institute, Harvard Medical School, Boston, MA, USA Search for more papers by this author Anne-Kathrin Wilbuer Anne-Kathrin Wilbuer Department of Cancer Immunology and AIDS, Dana Farber Cancer Research Institute, Harvard Medical School, Boston, MA, USA Program in Immunology, Harvard Medical School, Boston, MA, USA Search for more papers by this author Nilufer P Seth Nilufer P Seth Department of Cancer Immunology and AIDS, Dana Farber Cancer Research Institute, Harvard Medical School, Boston, MA, USA Search for more papers by this author Kai W Wucherpfennig Kai W Wucherpfennig Department of Cancer Immunology and AIDS, Dana Farber Cancer Research Institute, Harvard Medical School, Boston, MA, USA Program in Immunology, Harvard Medical School, Boston, MA, USA Department of Neurology, Harvard Medical School, Boston, MA, USA Search for more papers by this author John K McCormick John K McCormick Department of Microbiology and Immunology, Lawson Health Research Institute, University of Western Ontario, London, Ontario, Canada Search for more papers by this author David M Kranz David M Kranz Department of Biochemistry, University of Illinois, Urbana, IL, USA Search for more papers by this author Eric J Sundberg Corresponding Author Eric J Sundberg Boston Biomedical Research Institute, Watertown, MA, USA Search for more papers by this author Beenu Moza Beenu Moza Boston Biomedical Research Institute, Watertown, MA, USA Search for more papers by this author Ashok K Varma Ashok K Varma Boston Biomedical Research Institute, Watertown, MA, USA Search for more papers by this author Rebecca A Buonpane Rebecca A Buonpane Department of Biochemistry, University of Illinois, Urbana, IL, USA Search for more papers by this author Penny Zhu Penny Zhu Boston Biomedical Research Institute, Watertown, MA, USA Search for more papers by this author Christine A Herfst Christine A Herfst Department of Microbiology and Immunology, Lawson Health Research Institute, University of Western Ontario, London, Ontario, Canada Search for more papers by this author Melissa J Nicholson Melissa J Nicholson Department of Cancer Immunology and AIDS, Dana Farber Cancer Research Institute, Harvard Medical School, Boston, MA, USA Search for more papers by this author Anne-Kathrin Wilbuer Anne-Kathrin Wilbuer Department of Cancer Immunology and AIDS, Dana Farber Cancer Research Institute, Harvard Medical School, Boston, MA, USA Program in Immunology, Harvard Medical School, Boston, MA, USA Search for more papers by this author Nilufer P Seth Nilufer P Seth Department of Cancer Immunology and AIDS, Dana Farber Cancer Research Institute, Harvard Medical School, Boston, MA, USA Search for more papers by this author Kai W Wucherpfennig Kai W Wucherpfennig Department of Cancer Immunology and AIDS, Dana Farber Cancer Research Institute, Harvard Medical School, Boston, MA, USA Program in Immunology, Harvard Medical School, Boston, MA, USA Department of Neurology, Harvard Medical School, Boston, MA, USA Search for more papers by this author John K McCormick John K McCormick Department of Microbiology and Immunology, Lawson Health Research Institute, University of Western Ontario, London, Ontario, Canada Search for more papers by this author David M Kranz David M Kranz Department of Biochemistry, University of Illinois, Urbana, IL, USA Search for more papers by this author Eric J Sundberg Corresponding Author Eric J Sundberg Boston Biomedical Research Institute, Watertown, MA, USA Search for more papers by this author Author Information Beenu Moza1,‡, Ashok K Varma1, Rebecca A Buonpane2, Penny Zhu1, Christine A Herfst3, Melissa J Nicholson4, Anne-Kathrin Wilbuer4,5, Nilufer P Seth4, Kai W Wucherpfennig4,5,6, John K McCormick3, David M Kranz2 and Eric J Sundberg 1 1Boston Biomedical Research Institute, Watertown, MA, USA 2Department of Biochemistry, University of Illinois, Urbana, IL, USA 3Department of Microbiology and Immunology, Lawson Health Research Institute, University of Western Ontario, London, Ontario, Canada 4Department of Cancer Immunology and AIDS, Dana Farber Cancer Research Institute, Harvard Medical School, Boston, MA, USA 5Program in Immunology, Harvard Medical School, Boston, MA, USA 6Department of Neurology, Harvard Medical School, Boston, MA, USA ‡These authors contributed equally to this work *Corresponding author. Boston Biomedical Research Institute, 64 Grove Street, Watertown, MA 02472, USA. Tel.: +1 617 658 7882; Fax: +1 617 972 1761; E-mail: [email protected] The EMBO Journal (2007)26:1187-1197https://doi.org/10.1038/sj.emboj.7601531 PDFDownload PDF of article text and main figures. ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions Figures & Info Superantigens (SAGs) bind simultaneously to major histocompatibility complex (MHC) and T-cell receptor (TCR) molecules, resulting in the massive release of inflammatory cytokines that can lead to toxic shock syndrome (TSS) and death. A major causative agent of TSS is toxic shock syndrome toxin-1 (TSST-1), which is unique relative to other bacterial SAGs owing to its structural divergence and its stringent TCR specificity. Here, we report the crystal structure of TSST-1 in complex with an affinity-matured variant of its wild-type TCR ligand, human T-cell receptor β chain variable domain 2.1. From this structure and a model of the wild-type complex, we show that TSST-1 engages TCR ligands in a markedly different way than do other SAGs. We provide a structural basis for the high TCR specificity of TSST-1 and present a model of the TSST-1-dependent MHC–SAG–TCR T-cell signaling complex that is structurally and energetically unique relative to those formed by other SAGs. Our data also suggest that protein plasticity plays an exceptionally significant role in this affinity maturation process that results in more than a 3000-fold increase in affinity. Introduction Bacterial superantigens (SAGs) comprise a large family of disease-associated proteins that are produced primarily by Staphylococcus aureus and Streptococcus pyogenes (McCormick et al, 2001). SAGs function by simultaneously interacting with major histocompatibility complex (MHC) class II and T-cell receptor (TCR) molecules on antigen-presenting cells (APCs) and T lymphocytes, respectively (Sundberg et al, 2002b). Contrary to processed antigenic peptides, SAGs bind to MHC molecules outside of their peptide-binding grooves and interact only with the Vβ domains of TCRs, resulting in the stimulation of up to 20% of the entire T-cell population. In this way, SAGs initiate a systemic release of inflammatory cytokines that results in a condition known as toxic shock syndrome (TSS) and can ultimately lead to multi-organ failure and death. Toxic shock syndrome toxin-1 (TSST-1), an exotoxin secreted by S. aureus, was identified as a major causative agent of TSS some 25 years ago (Bergdoll et al, 1981; Schlievert et al, 1981). TSST-1 is unique in several respects in relation to other members of the family of SAGs, including its structural divergence and its TCR Vβ specificity. TSST-1 interacts almost exclusively with the human T-cell receptor β chain variable domain 2.1 (hVβ2) family (Choi et al, 1989), and a significant fraction of patients with TSS exhibit substantially expanded hVβ2+ T-cell populations (Choi et al, 1990). Although TSST-1 has been characterized extensively, the molecular mechanism by which it interacts specifically with TCR molecules and initiates the onset of TSS remains unclear. The binding sites on MHC molecules with which SAGs interact are diverse and can be classified into three distinct groups: (i) a site on the MHC α subunit entirely peripheral to the MHC-bound peptide; (ii) a zinc-mediated site on the MHC β subunit that extends over the MHC-bound peptide; and (iii) a site on the MHC α subunit that extends over the MHC-bound peptide. These three binding modes have been characterized crystallographically and are most readily exemplified by the SAGs staphylococcal enterotoxin B (SEB) (Jardetzky et al, 1994), streptococcal pyrogenic exotoxin C (SpeC) (Li et al, 2001) and TSST-1 (Kim et al, 1994), respectively. Crystal structures of SEB (Li et al, 1998) and SpeC (Sundberg et al, 2002a) with their respective TCR Vβ ligands have revealed that SAG-Vβ interactions are also structurally diverse. These structures have allowed for the construction of models of the ternary MHC–SAG–TCR supramolecular complexes required for SAG-mediated T-cell activation, which have been verified biochemically (Andersen et al, 1999) and characterized energetically (Andersen et al, 2002). As there is not a structure of the complex formed between TSST-1 (the only representative of the third MHC binding mode described above) and its Vβ ligand, the compendium of MHC–SAG–TCR signaling complexes that initiate SAG-induced disease remains incomplete. Despite the intense research efforts that have been directed toward the characterization of SAGs, therapeutics capable of neutralizing SAG-mediated T-cell activation in humans are unavailable. Intravenously administered pooled human immunoglobulin (IVIG) has been used with some success, but its supply is limited and its effectiveness is variable (Kaul et al, 1999; LeClaire and Bavari, 2001). Mouse monoclonal antibodies have been generated against SEB (Hamad et al, 1994; Pang et al, 2000), but have not been humanized for clinical use. A potentially more general anti-inflammatory agent, a recombinant cell-penetrating form of the suppressor of cytokine signaling 3, has exhibited some efficacy in protecting mice challenged with lethal doses of SEB (Jo et al, 2005). Thus, we have pursued a strategy of using affinity-matured forms of TCR Vβ domains, the natural receptors of the toxins, as potential therapeutics. To date, we have engineered Vβ domain-derived SAG antagonists that bind to their SAG targets, including staphylococcal enterotoxin C3 (SEC3), SEB and TSST, with affinities up to a million-fold higher than the wild-type SAG-Vβ interactions (Kieke et al, 2001; Buonpane et al, 2005). One of these Vβ variants completely neutralizes the lethal activity of SEB in animal models (unpublished results). Beyond engineering anti-SAG therapeutics, the affinity maturation of a drug target's natural ligand to create a competitive inhibitor may constitute a generally applicable approach to therapeutic development. An additional benefit of such an approach to developing therapeutics is that they provide model systems for understanding the molecular basis of protein–protein interactions generally. Energetic and structural dissection of the affinity maturation pathways defined by these evolved protein complexes provides insights into the molecular determinants that govern the specificities and affinities of molecular interactions. As the affinity maturation process required for such large differences in SAG affinity between the wild-type and penultimate variant Vβ domains is necessarily dependent on combinations of mutations, these model systems are especially useful for quantifying those biophysical parameters that are combinatorial in nature, such as cooperativity and plasticity (i.e., conformational flexibility), and therefore beyond the scope of investigations using standard site-directed mutagenesis techniques. Accordingly, we have performed structural and thermodynamic analyses of affinity-matured Vβ-SAG molecular systems that have provided novel insights into the molecular bases of energetic cooperativity and additivity in protein–protein interactions (Yang et al, 2003; Cho et al, 2005; Moza et al, 2006). Here, we present the X-ray crystal structure of TSST-1 in complex with D10, the penultimate affinity-matured variant of the hVβ2.1 whose affinity for TSST-1 is three orders of magnitude higher than that of wild-type hVβ2.1 (Buonpane et al, 2005). From this structure, we have modeled the wild-type TSST-1–hVβ2.1 complex structure, which is completely consistent with mutational analysis of wild-type residues in both TSST-1 (McCormick et al, 2003) and hVβ2.1 (Buonpane et al, 2005). These structures show that TSST-1 engages its TCR ligand in a structurally unique way relative to other SAGs. Additionally, they provide a molecular basis for the stringent specificity of TSST-1 and a model of the MHC–TSST-1–TCR ternary complex that is a structural and energetic hybrid of the SpeC- and SEB-dependent supramolecular T-cell signaling complexes. Finally, these data suggest that instead of increases in intermolecular contacts and buried surface area, protein plasticity may be primarily responsible for this greater than 3000-fold increase in affinity for a protein–protein interaction. Results and discussion Unique TCR engagement by a bacterial superantigen We have determined the X-ray crystal structure of TSST-1 in complex with the high-affinity hVβ2.1 variant D10 (Figure 1A, left panel). The structure was solved by molecular replacement methods using the wild-type TSST-1 (Prasad et al, 1997) and hVβ2.1 (Sundberg et al, 2002a) structures as search models. The structure of the complex has been refined to a resolution of 2.25 Å. Data collection and refinement statistics are shown in Table I. The docking orientation of the two molecules in this complex is similar to that of a model of this interaction that we proposed previously based on mutagenesis analysis (Moza et al, 2006). Not only does the high-resolution X-ray crystal structure of the TSST-1–D10 complex reported here verify our previous model, but it also provides details of the molecular contacts within the interface at the atomic level and reveals the flexible nature of this region of the hVβ2.1 molecule. These observations are critical for understanding SAG–TCR specificity and cross-reactivity, as well as the role of protein plasticity in SAG–TCR engagement, respectively. Figure 1.Distinct SAG-binding sites on a common ligand. (A) Crystal structure of the TSST-1–D10 complex (left panel) and a model of the wild-type TSST-1–hVβ2.1 complex (right panel). TSST-1 is in yellow; hVβ2.1 is in green. The side chains of the residues that are mutated in D10 relative to wild-type hVβ2.1 are shown. Those mutations that are energetically significant are in magenta; the remaining mutations are in green. (B) Superposition of the TSST-1–hVβ2.1 and SpeC–hVβ2.1 complexes. The hVβ2.1 molecule belonging to the SpeC–hVβ2.1 complex has been removed for clarity. Color coding is as in (A); SpeC is in cyan. (C) Molecular surface of hVβ2.1 buried uniquely by TSST-1 (yellow) or SpeC (cyan) and the shared portion of the epitope (magenta). The hVβ2.1 molecule in (C) has been rotated approximately 90° clockwise about the vertical axis of the page relative to its orientation in (A) and (B). Download figure Download PowerPoint Table 1. Structure determination and refinement statistics Data collection and processing Space group C2 Unit cell dimensions a (Å) 190.9 b (Å) 68.4 c (Å) 53.5 b (deg) 106.2 Resolution (Å) 2.25 Molecules/asymmetric unit 2 TSST-1/2 D10 Observations 180 278 Unique reflections 32 180 Completeness (%)a 99.4 (99.1) Redundancya 5.6 (5.3) Rsym (%)b 7.4 (25.0) Mean I/σ(I) 21.5 (7.2) Refinement Rcryst (%)c 24.23 Rfree (%)d 25.16 Protein residues 612 Water molecules 237 Ramachandran plot statistics Core (%) 85.8 Allowed (%) 11.4 Generous (%) 2.6 Disallowed (%) 0.2 R.m.s. deviations from ideality Bonds (Å) 0.019 Angles (deg) 1.807 a Values in parentheses are for the highest resolution shell (2.29–2.25 Å). b Rsym=∑∣((Ihkl−I(hkl))∣/(∑Ihkl), where I(hkl) is the mean intensity of all reflections equivalent to hkl by symmetry. c Rcryst=∑∣∣FO∣−∣FC∣/∑∣FO∣∣, where FC is the calculated structure factor. d Rfree is calculated over reflections in a test set not included in atomic refinement using 4.6% of the reflections chosen at random and omitted from the refinement calculations. D10 binds TSST-1 with an affinity more than 3000-fold tighter than wild-type hVβ2.1 (KD=180 pM and 600 nM, respectively), and was engineered by yeast display as a potential protein therapeutic for TSST-1-mediated disease (Buonpane et al, 2005). D10 contains 13 mutations, but only four of these (E51Q, S52aF, K53N and E61V) have been shown to be energetically significant (Moza et al, 2006). Although we and others have previously crystallized the wild-type TSST-1–hVβ2.1 complex, the quality of such crystals has not been sufficient to allow the determination of its atomic structure. Thus, using the TSST-1–D10 crystal structure, we produced a molecular model of the complex between TSST-1 and wild-type hVβ2.1 using CNS (Brunger et al, 1998), as described in the Materials and methods section. The modeled TSST-1–hVβ2.1 complex structure is shown (Figure 1A, right panel). The docking orientation of the two molecules that comprise the TSST-1–D10 and TSST-1–hVβ2.1 complexes is virtually identical, and has been independently verified by numerous mutagenesis studies (McCormick et al, 2003; Buonpane et al, 2005; Moza et al, 2006). TSST-1 engages hVβ2.1 primarily through intermolecular contacts with residues from the second complementarity determining region (CDR2) loop and the third framework region (FR3). No contacts with residues from the CDR1, CDR3 or HV4 loops are made with TSST-1. Although D10 incorporated four mutations relative to wild-type hVβ2.1 in its CDR1 loop (Buonpane et al, 2005), none of these mutations affected binding to TSST-1 significantly (Moza et al, 2006), in accordance with the complex structure. In total, the modeled wild-type TSST-1–hVβ2.1 complex includes 1917 Å2 of buried surface area, which is similar to the SpeC–hVβ2.1 complex (Sundberg et al, 2002a), but significantly greater than that buried by either SEB, SEC3 or streptococcal pyrogenic exotoxin A (SpeA) with murine T-cell receptor β chain variable domain 8.2 (mVβ8.2) (Fields et al, 1996; Li et al, 1998; Sundberg et al, 2002a). Of the other SAGs that are known to bind hVβ2.1, only the co-crystal structure with SpeC has been determined (Sundberg et al, 2002a). TSST-1 and SpeC have been shown previously to compete for binding to wild-type hVβ2.1 (Buonpane et al, 2005). The overlap between the TSST-1- and SpeC-binding interfaces with their mutual TCR ligand, however, is minimal (Figure 1B and C). The common residues engaged by TSST-1 and SpeC numbers only five, out of a total of 13 and 18 hVβ2.1 residues contacted by these two SAGs, respectively. All of these common residues reside in the CDR2 loop. The only other region of hVβ2.1 that TSST-1 binds is FR3. In fact, TSST-1 interacts with a single contiguous stretch of the hVβ2.1 sequence, spanning from residues 51 to 64 and including the CDR2 loop, the c″ β-strand and FR3. In contrast, SpeC engages discreet stretches of the hVβ2.1 sequence, namely those that comprise the apical regions of the CDR1, CDR2, HV4 and CDR3 loops. Additionally, SpeC makes no intermolecular contacts with FR3 residues in the apex of the loop situated between the CDR2 and HV4 loops (i.e., residues 58–64). Instead, SpeC contacts only those FR3 residues that are contiguous with and adjacent to the CDR2 (i.e., position 55) and HV4 (i.e., positions 67 and 68) loops. The consequence of these differential intermolecular contacts between TSST-1 and SpeC for their common TCR ligand is that TSST-1 binds the surface of hVβ2.1 that is shifted away from the major hypervariable elements that bind peptide-MHC (pMHC) complexes (Hahn et al, 2005), and distinct from the surface that binds SpeC, which is more toward the Cβ domain of the TCR. The docking orientation of TSST-1 on hVβ2.1 is also markedly different than that of SEB binding to mVβ8.2, which is more similar to the SpeC–hVβ2.1 complex (Li et al, 1998). This unique TCR engagement by TSST-1 has important ramifications for its TCR specificity and the formation of the TSST-1-dependent supramolecular T-cell signaling complex, as discussed below. Chemical basis of the stringent TCR specificity of TSST-1 TSST-1 is the most specific bacterial SAG known, stimulating only Vβ2+ T cells (Choi et al, 1990). Our structure of the TSST-1–D10 complex, and subsequent model of the TSST-1 complex with wild-type hVβ2.1, reveals the molecular basis for this binding specificity. It seems counterintuitive that, among known SAG–TCR structures, TSST-1 utilizes contacts involving the smallest proportion of hypervariable sequences of the TCR Vβ domain (Figure 1C), but is nonetheless the most specific of any SAG–TCR complex. The complete lack of influence on binding of the CDR1 loop, as shown by our structure, previous mutagenesis (Buonpane et al, 2005) and binding analyses (Moza et al, 2006), is particularly surprising because this CDR loop contains a noncanonical single residue insertion unique to the highly homologous hVβ2 and hVβ4 domains. Conversely, T cells bearing both of these TCR Vβ domains are efficiently stimulated by SpeC (Li et al, 1997), and contacts with CDR1 loop residues specifically have been shown to be important for such T-cell activation (Rahman et al, 2006). The CDR2 loops of hVβ2 and hVβ4 are nearly identical in sequence. If TSST-1-mediated T-cell activation was dependent only on the sequence and structure of the CDR and HV loops of the TCR β chain, as it is with pMHC complexes and other SAGs, then why does TSST-1 not stimulate many other subsets of T cells and what dictates the fine specificity of TSST-1 such that it does not activate even hVβ4+ T cells? Beyond the CDR2 loop, many of the intermolecular contacts formed by TSST-1 in this complex (Figure 2A) are made with residues that are unique to hVβ2.1. These residues reside primarily in the FR3 loop, which connects the c″ and d β-strands in TCR Vβ domains. In hVβ2.1, this loop is longer than it is in most TCR Vβ domains and consequently adopts a conformation that is structurally distinct relative to other simple β-turn elements that comprise other FR3 loops (Figure 2B). This is the case whether the Vβ domain exhibits the conventional immunoglobulin (Ig) fold β-strand topology in which the c″ β-strand is hydrogen bonded to the preceding c′ β-strand, and is found in hVβ2.1 and mVβ8.2 (Figure 2B, left panel), or in strand-swapped Vβ domains in which the c″ β-strand hydrogen bonds to the succeeding d β-strand, as in murine T-cell receptor β chain variable domain 2.3 (mVβ2.3) (Figure 2B, right panel). Within the c″ β-strand, one residue, Tyr56, which is unique to hVβ2.1 and hVβ4.1 among all Vβ domains, was found to have the most significant effect on TSST-1 binding when mutated to alanine (Buonpane et al, 2005). Figure 2.Structural features responsible for SAG–TCR specificity. (A) The TSST-1–hVβ2.1 complex with the CDR2 and FR3 hot regions demarcated. Upper inset, close-up of the molecular interactions in the FR3 hot region. Lower inset, close-up of the molecular interactions in the CDR2 hot region. Only residues that form contacts are drawn. Color coding is as in Figure 1A. (B) Superposition of the c′, c″ and d β-strands including the CDR2 and FR3 of hVβ2.1 with mVβ8.2 (left panel) and with mVβ2.3 (right panel). The side chains of Pro61 in both mVβ8.2 and mVβ2.3 are shown. Colors are as follows: hVβ2.1, green; mVβ8.2, cyan; mVβ2.3, magenta. Download figure Download PowerPoint Two residues in particular in the hVβ2.1 FR3, Glu61 and Lys62, which are known hot spots for TSST-1 interaction (Buonpane et al, 2005; Moza et al, 2006), are critical for the stringent specificity of TSST-1. Approximately three quarters of all human TCR Vβ domains contain a proline residue at position 61, which disallows the unique conformation adopted by the FR3 loop of hVβ2.1 (Figure 2B). Additionally, half of all human TCR Vβ domains lack a residue at position 62. Together, these sequence differences in, and their resulting constraints on, FR3 explain why TSST-1 does not bind the great majority of Vβ domains nor stimulate those T cells bearing such. The fine specificity of TSST-1, by which it distinguishes between hVβ2 and hVβ4, depends, instead, on which amino acids are indeed present at positions 61 and 62. In hVβ4, residue 61 is a Val, as opposed to a Glu in hVβ2. Surprisingly, this is a mutation that is found in D10 as well, and we have shown previously that this single-site mutation in the hVβ2.1 wild-type background significantly enhances affinity for TSST-1 (Moza et al, 2006). Thus, TSST-1 would be expected to bind hVβ4 exceptionally well on account of the similarity of the CDR2 loop and this sequence difference at position 61. However, residue 62 is an Ile in hVβ4 instead of a Lys in hVβ2. Residue Lys62 is arguably one of the most important residues for TSST-1 interaction (the other being Tyr56) as it is a known hot spot residue (Buonpane et al, 2005). In our modeled wild-type TSST-1–hVβ2.1 complex, Lys62 makes 20 van der Waals interactions and three hydrogen bonds with numerous TSST-1 residues, and buries a total of 116 Å2 surface area, all of which are by far the most of any residue in hVβ2.1. Thus, we propose that the fine specificity of TSST-1 for TCR Vβ domains is dependent primarily on the presence of a Lys residue at position 62. The selective engagement of TSST-1 with hVβ2.1 is further dependent on the particular arrangement of these intermolecular contacts, namely the alignment of hot regions (i.e., clusters or modules of hot spot residues; Keskin et al, 2005; Reichmann et al, 2005) from these two proteins. Numerous mutagenesis studies have been carried out involving this protein–protein interaction, leading to a detailed mapping of the energetic contributions of residues found within the molecular interface (McCormick et al, 2003; Buonpane et al, 2005; Moza et al, 2006). The structure of the TSST-1–hVβ2.1 complex reveals the perfect juxtaposition of hot regions from each side of the interface: TSST-1 residues within a hot region composed primarily of residues from the central α-helix contact hVβ2.1 hot spots clustered in the apical loop of FR3 (Figure 2A, upper close-up); TSST-1 hot spots in the α1–β1 and β5–β6 loops contact the hVβ2.1 CDR2 loop hot region (Figure 2A, lower close-up). Specificity of the TSST-1–hVβ2.1 complex is further enhanced by the fact that each of the TSST-1 contact residues shares essentially no homology with residues at the same positions in other SAGs. Even analogous residues from TSST-1 and SpeC that both form intermolecular contacts with hVβ2.1, their common TCR ligand, are entirely dissimilar. Whereas wild-type hVβ2.1 binds both TSST-1 and SpeC, the affinity-matured hVβ2.1 variant D10 binds only to TSST-1. In the SpeC–hVβ2.1 complex, the SpeC residues Tyr15 and Arg181 each make hydrogen-bonding interactions with the hVβ2.1 residue Ser52a, sandwiching this noncanonical CDR2 insertion residue (Sundberg et al, 2002a). Essentially all of the binding energy of the SpeC–hVβ2.1 complex is concentrated in the particular structural arrangement of these three residues (Rahman et al, 2006). D10, with its S52aF mutation, could not be sterically accommodated by the Tyr15SpeC and Arg181SpeC hot spot residues. Structural basis of superantigen cross-reactivity and specificity Our TSST-1–hVβ2.1 structure provides a key addition to the still small database of SAG–TCR complex structures (Fields et al, 1996; Li et al, 1998; Sundberg et al, 2002a). As TSST-1 exhibits the highest TCR Vβ domain specificity of any SAG, our analysis contributes significantly to the growing model of SAG cross-reactivity and specificity. Although all SAGs bind the Vβ CDR2 loop, how structural changes within this and other hypervariable, as well as certain framework, regions of TCR Vβ domains dictate the specificity of SAG–TCR interactions is beginning to emerge. The least specific SAGs (including SEB and SEC3) depend primarily on a common conformation adopted by the CDR2 and HV4 loops in many Vβ domains (Fields et al, 1996; Li et al, 1998). In these complexes, hydrogen bonds are made only to Vβ main-chain atoms, such that numerous combinations of amino-acid sequences in CDR2 and HV4 can satisfy the binding requirements for these SAGs, as long as they do not change the lengths of these hypervariable loops nor disrupt the common structural conformation adopted. As TCR specificity increases (e.g., SpeA), the number of hypervariable loops with which the SAG interacts increases beyond CDR2 and HV4. Additionally, the interface becomes increasingly populated by hydrogen bonds formed directly between side-chain atoms from both SAG and TCR (Sundberg et al, 2002a). As TCR Vβ domain-binding partners become restricted even further (e.g., SpeC), the engagement of the entire repertoire of TCR hypervariable elements is observed. The CDR loops with which the SAG int" @default.
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• W2143157762 title "Structural basis of T-cell specificity and activation by the bacterial superantigen TSST-1" @default.
• W2143157762 cites W1539796472 @default.
• W2143157762 cites W1559347919 @default.
• W2143157762 cites W1965560540 @default.
• W2143157762 cites W1970269406 @default.
• W2143157762 cites W1988899912 @default.
• W2143157762 cites W1991084507 @default.
• W2143157762 cites W1992743196 @default.
• W2143157762 cites W1995017064 @default.
• W2143157762 cites W1995134733 @default.
• W2143157762 cites W1996621120 @default.
• W2143157762 cites W2002112906 @default.
• W2143157762 cites W2013760221 @default.
• W2143157762 cites W2016765195 @default.
• W2143157762 cites W2025067737 @default.
• W2143157762 cites W2029099352 @default.
• W2143157762 cites W2032699989 @default.
• W2143157762 cites W2032733534 @default.
• W2143157762 cites W2041526132 @default.
• W2143157762 cites W2044682925 @default.
• W2143157762 cites W2046248566 @default.
• W2143157762 cites W2049340046 @default.
• W2143157762 cites W2058700616 @default.
• W2143157762 cites W2071743575 @default.
• W2143157762 cites W2073939564 @default.
• W2143157762 cites W2076657373 @default.
• W2143157762 cites W2082660881 @default.
• W2143157762 cites W2084519264 @default.
• W2143157762 cites W2084612387 @default.
• W2143157762 cites W2101272434 @default.
• W2143157762 cites W2101364960 @default.
• W2143157762 cites W2106481565 @default.
• W2143157762 cites W2113118666 @default.
• W2143157762 cites W2113575403 @default.
• W2143157762 cites W2115156437 @default.
• W2143157762 cites W2116566944 @default.
• W2143157762 cites W2121433760 @default.
• W2143157762 cites W2125823078 @default.
• W2143157762 cites W2131272563 @default.
• W2143157762 cites W2132164302 @default.
• W2143157762 cites W2135839939 @default.
• W2143157762 cites W2140386129 @default.
• W2143157762 cites W2144081223 @default.
• W2143157762 cites W2147774237 @default.
• W2143157762 cites W2150345297 @default.
• W2143157762 cites W2151546364 @default.
• W2143157762 cites W2157417177 @default.
• W2143157762 cites W2165319219 @default.
• W2143157762 cites W2167010459 @default.
• W2143157762 cites W4245799938 @default.
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