Crystal structure of a biologically inactive mutant of toxic shock syndrome toxin-1 at 2.5 A resolution (original) (raw)
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The Refined Crystal Structure of Toxic Shock Syndrome Toxin-1 at 2.07 Å Resolution
Journal of Molecular Biology, 1996
of aureus is a causative agent of the toxic shock syndrome disease. It belongs to a family of proteins known as superantigens that cross-link major Bath, Claverton Down, Bath histocompatibility class II molecules and T-cell receptors leading to the BA2 7AY, UK activation of a substantial number of T cells. The crystal structure of this 2 Developmental Production protein has been refined to 2.07 Å with an R cryst value of 20.4% for 51,240 Department, Production reflections. The final model contains three molecules in the asymmetric Division, Centre for Applied unit with good stereochemistry and a root-mean-square deviation of Microbiology and Research 0.009 Å and 1.63°from ideality for bond lengths and bond angles, Porton Down, Salisbury respectively. The overall fold is considerably similar to that of other SP4 0JG, UK known microbial superantigens (staphylococcal enterotoxins). However, a detailed structural analysis shows that toxic shock syndrome toxin-1 lacks several structural features that affect its specificity for Vb elements of the T-cell receptor and also its recognition by major histocompatibility class II molecules.
European Journal of Immunology, 1995
Superantigens bind to major histocompatibility complex (MHC) class II proteins and interact with variable parts of the T cell antigen receptor (TCR) beta-chain. Cross-linking the TCR with MHC class II molecules on the antigen-presenting cell by the superantigen leads to T cell activation that plays an essential role in pathogenesis. Recent crystallographic data have resolved the structure of the complexes between HLA-DR1 and staphylococcal enterotoxin B (SEB) and toxic shock syndrome toxin-1 (TSST-1), respectively. For TSST-1, these studies have revealed possible contact sites between the superantigen and the HLA-DR1-bound peptide. Here, we show that TSST-1 binding is dependent on the MHC-II-associated peptides by employing variants of T2 mutant cells deficient in loading of peptides to MHC class II molecules as superantigen-presenting cells. On HLA-DR3-transfected T2 cells, presentation of TSST-1, but not SEB, was dependent on HLA-DR3-associated peptides. Thus, although these superantigens can be recognized in the context of multiple MHC class II alleles and isotypes, they clearly bind to specific subsets of MHC molecules displaying appropriate peptides.
Proteins: Structure, Function, and Bioinformatics, 2007
The illnesses associated with bacterial superantigens (SAgs) such as food poisoning and toxic shock syndrome, as well as the emerging threat of purpura fulminans and community-associated methicillin-resistant S. aureus producer of SAgs, emphasize the importance of a better characterization of SAg binding to their natural ligands, which would allow the development of drugs or biological reagents able to neutralize their action. SAgs are toxins that bind major histocompatibility complex class II molecules (MHC-II) and T-cell receptors (TCR), in a nonconventional manner, inducing T-cell activation that leads to production of cytokines such as tumor necrosis factor and interleukin-2, which may result in acute toxic shock. Previously, we cloned and expressed a new natural variant of staphylococcal enterotoxin G (SEG) and evaluated its ability to stimulate in vivo murine T-cell subpopulations. We found an early, strong, and widespread stimulation of mouse Vb8.2 T-cells when compared with other SAgs member of the SEB subfamily. In search for the reason of the strong mitogenic potency, we determined the SEG crystal structure by X-ray crystallography to 2.2 Å resolution and analyzed SEG binding to mVb8.2 and MHC-II. Calorimetry and SPR analysis showed that SEG has an affinity for mVb8.2 40 to 100-fold higher than that reported for other members of SEB subfamily, and the highest reported for a wild type SAg-TCR couple. We also found that mutations introduced in mVb8.2 to produce a high affinity mutant for other members of the SEB subfamily do not greatly affect binding to SEG. Crystallographic analysis and docking into mVb8.2 in complex with SEB, SEC3, and SPEA showed that the deletions and substitution of key amino acids remodeled the putative surface of the mVb8.2 binding site without affecting the binding to MHC-II. This results in a SAg with improved binding to its natural ligands, which may confer a possible evolutionary advantage for bacterial strains expressing SEG. Proteins 2007;68:389-402. V V C 2007 Wiley-Liss, Inc.
Pasteur Institute of Iran, 2020
The development of a vaccine against Staphylococcus aureus has proven to be much more difficult than expected. In this study, we considered and analyzed a mutant Toxic Shock Syndrome Toxin-1 (TSST-1) as a potential vaccine candidate. Methods: An NCBI sequence of TSST-1 was analyzed bioinformatically by online tools such as Ensemble and Pubmlst. The protein sequence of TSST-1 was similarly analysed by Expasy ProtParam, Phyre2 and Vaxign databases. The protein functional class was predicted by VICMpred database while the Band T-cell epitopes were predicted by IEDB and BepiPred tools. The 3D structure was predicted by LOMETS, QMEAN, ProSA-web and ElliPro. The conservation of the epitopes was evaluated by ConSurf tool. Results: In silico analyses showed that this protein is present in high-prevalence sequence types of circulating clinical strains. It appears that TSST-1 has conserved liner and conformational B-cell epitopes. In addition, there are four potent of T-cell epitopes in this protein. Conclusion: This in silico data indicated that TSST-1 (and especially amino acid residues 81-221) is a promising vaccine target against S. aureus.
Immunology, 1998
A number of investigators have utilized a variety of methods to identify the structural basis for the interaction of superantigens with the T-cell receptor b-chain. The previous studies strongly suggest that a region of the toxin near residues N23, Y61, Y91 and D209 is important for this binding activity. Examination of crystal structure data shows that these residues line the rim of one side of a shallow cavity in the toxin. In an attempt further to define the face of the staphylococcal enterotoxin B (SEB) molecule involved in the interaction with the b-chain, we have employed a polymerase chain reaction (PCR)-based, site-specific mutagenesis method to generate amino acid substitutions of residues on the opposite side of this putative T-cell receptor interaction cavity. Our results show that Y175 and N179 appear to be involved in the function of this superantigen, since each of several substitutions at this position exhibits a significantly reduced ability to induce T-cell proliferation. At the same time, mutation of the proximal Y186 does not alter the superantigen activity of SEB. Binding analysis of these mutants shows that class II binding activity is not significantly altered. Analysis of the responding T cells shows that the mutant toxins maintain T-cell receptor Vb selectivity. However, responses of T cells bearing the Vb8.1 allele appear to be particularly diminished. When viewed in the context of other results reported in the literature, our results suggest that the T-cell receptor interaction site involves SEB residues which ring both the Y175/N179-side and the N23-side of a cavity on one side of the toxin molecule.
Protein Science, 1997
The structure of toxic shock syndrome toxin-1 (TSST-I), the causative agent in toxic shock syndrome, has been determined in three crystal forms. The three structural models have been refined to R-factors of 0.154, 0.150, and 0.198 at resolutions of 2.05 A, 2.90 A, and 2.75 A, respectively. One crystal form of TSST-I contains a zinc ion bound between two symmetry-related molecules. Although not required for biological activity, zinc dramatically potentiates the mitogenicity of TSST-1 at very low concentrations. In addition, the structure of the tetramutant TSST-IH [T69I, YSOW, E132K, 114OT1, which is nonmitogenic and does not amplify endotoxin shock, has been determined and refined in a fourth crystal form (R-factor = 0.173 to 1.9 A resolution).
Journal of Biological Chemistry, 2006
Superantigens are bacterial or viral proteins that elicit massive T cell activation through simultaneous binding to major histocompatibility complex (MHC) class II and T cell receptors. This activation results in uncontrolled release of inflammatory cytokines, causing toxic shock. A remarkable property of superantigens, which distinguishes them from T cell receptors, is their ability to interact with multiple MHC class II alleles independently of MHC-bound peptide. Previous crystallographic studies have shown that staphylococcal and streptococcal superantigens belonging to the zinc family bind to a high affinity site on the class II β-chain. However, the basis for promiscuous MHC recognition by zinc-dependent superantigens is not obvious, because the β-chain is polymorphic and the MHC-bound peptide forms part of the binding interface. To understand how zinc-dependent superantigens recognize MHC, we determined the crystal structure, at 2.0 Å resolution, of staphylococcal enterotoxin I bound to the human class II molecule HLA-DR1 bearing a peptide from influenza hemagglutinin. Interactions between the superantigen and DR1 β-chain are mediated by a zinc ion, and 22% of the buried surface of peptide·MHC is contributed by the peptide. Comparison of the staphylococcal enterotoxin I·peptide·DR1 structure with ones determined previously revealed that zinc-dependent superantigens achieve promiscuous binding to MHC by targeting conservatively substituted residues of the polymorphic β-chain. Additionally, these superantigens circumvent peptide specificity by engaging MHC-bound peptides at their conformationally conserved N-terminal regions while minimizing sequence-specific interactions with peptide residues to enhance crossreactivity.
Protein Science, 2009
Staphylococcal enterotoxins (SEs) are superantigenic protein toxins responsible for a number of lifethreatening diseases. The X-ray structure of a staphylococcal enterotoxin A (SEA) triple-mutant (L48R, D70R, and Y92A) vaccine reveals a cascade of structural rearrangements located in three loop regions essential for binding the ␣ subunit of major histocompatibility complex class II (MHC-II) molecules. A comparison of hypothetical model complexes between SEA and the SEA triple mutant with MHC-II HLA-DR1 clearly shows disruption of key ionic and hydrophobic interactions necessary for forming the complex. Extensive dislocation of the disulfide loop in particular interferes with MHC-II␣ binding. The triple-mutant structure provides new insights into the loss of superantigenicity and toxicity of an engineered superantigen and provides a basis for further design of enterotoxin vaccines.
Growth and analysis of crystal forms of toxic shock syndrome toxin 1
Proteins: Structure, Function, and Genetics, 1993
Native toxic shock syndrome toxin 1 (TSST-1) purified from StaphyZococcus aureus has been crystallized in four different forms. The highest resolution data (2.05 A) was collected from orthorhombic crystals belonging to the space group C222,. The unit cell dimensions are a = 108.7 A, b = 177.5 A, c = 97.6 A. Rotation function analysis of this form indicates that there is trimer of toxin molecules in the asymmetric unit with a local 3-fold axis parallel to the crystallographic c axis. Crystals of a double mutant of TSST-1 have beeen grown which has a single molecule in the asymmetric unit and diffract to 1.9 8. The space group is P2, with unit cell parameters of a = 44.4 A, b = 34.0 A, c=55.2 A, p=93.0°. o 1993 Wiey-Lisa, h c .