A natural mutation of the amino acid residue at position 60 destroys staphylococcal enterotoxin A murine T-cell mitogenicity (original) (raw)
Related papers
T-cell antigen receptor binding sites for the microbial superantigen staphylococcal enterotoxin A
Proceedings of the National Academy of Sciences, 1992
We have examined the interaction of the microbial superantigen staphylococcal enterotoxin A (SEA) with peptides corresponding to overlapping regions of the T-cell antigen receptor (chain variable region V(33. SEA is known to stimulate murine T cells bearing certain VP3 elements, among them V(33. Five peptides were synthesized representing amino acids 1-24,20-44,39-60,57-77, and 74-95 of V.33. We demonstrate here that soluble VI33-bearing .8 chains can bind to a complex of SEA and major histocompatibility complex class II and that the synthetic peptide V(t33-(57-77) blocked this interaction. The peptide V.83-(57-77) also inhibited SEAinduced interferon-V production and SEA-induced proliferation of B1O.BR spleen cells. Conversely, the peptide corresponding to amino acids 57-77 of V.88.2, a VP3 element that is not recognized by SEA, decreased staphylococcal enterotoxin C-2-induced proliferation but did not affect SEA-induced proliferation. The peptide inhibition of SEA-induced function was due at least in part to inhibition of V(83-bearing T-cell activity, since the percentage of T cells reactive with an
The Journal of Immunology
Dimerization of MHC class II molecules on the cell surface of human THP-1 monocytic cell line is a requirement for staphylococcal superantigen (SAG)-induced cytokine gene expression. The capacities of various SAG to induce this response are governed by their modes of interaction with MHC class II molecules. Staphylococcal enterotoxin A (SEA), with its two binding sites, dimerizes MHC class II molecules and subsequently induces cytokine gene expression in THP-1 cells. Here, we demonstrate that staphylococcal enterotoxin D (SED) and staphylococcal enterotoxin E (SEE) induce, similarly, IL-1β and TNF-α gene expression in these cells. Using mutated toxins that lost their binding site with the MHC class II α- or β-chain, we demonstrate that this response is also mediated by the dimerization of MHC class II molecules through two binding sites. Furthermore, SED forms Zn2+-dependent homodimers that allow multiple modes of MHC class II clustering, including ligation of α-chains (α/α), β-chai...
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.
Journal of Experimental Medicine, 1998
The three-dimensional structure of the complex between a T cell receptor (TCR)  chain (mouse V  8.2J  2.1C  1) and the superantigen (SAG) staphylococcal enterotoxin C3 (SEC3) has been recently determined to 3.5 Å resolution. To evaluate the actual contribution of individual SAG residues to stabilizing the  -SEC3 complex, as well as to investigate the relationship between the affinity of SAGs for TCR and MHC and their ability to activate T cells, we measured the binding of a set of SEC3 and staphylococcal enterotoxin B (SEB) mutants to soluble recombinant TCR  chain and to the human MHC class II molecule HLA-DR1. Affinities were determined by sedimentation equilibrium and/or surface plasmon detection, while mitogenic potency was assessed using T cells from rearrangement-deficient TCR transgenic mice. We show that there is a clear and simple relationship between the affinity of SAGs for the TCR and their biological activity: the tighter the binding of a particular mutant of SEC3 or SEB to the TCR  chain, the greater its ability to stimulate T cells. We also find that there is an interplay between TCR-SAG and SAG-MHC interactions in determining mitogenic potency, such that a small increase in the affinity of a SAG for MHC can overcome a large decrease in the SAG's affinity for the TCR. Finally, we observe that those SEC3 residues that make the greatest energetic contribution to stabilizing the  -SEC3 complex ("hot spot" residues) are strictly conserved among enterotoxins reactive with mouse V  8.2, thereby providing a basis for understanding why SAGs having other residues at these positions show different V binding specificities.
The Journal of experimental medicine, 1994
Bacterial and retroviral superantigens (SAGs) stimulate a high proportion of T cells expressing specific variable regions of the T cell receptor (TCR) beta chain. Although most alleles and isotypes bind SAGs, polymorphisms of major histocompatibility complex (MHC) class II molecules affect their presentation to T cells. This observation has raised the possibility that a TCR-MHC class II interaction can occur during this recognition process. To address the importance of such interactions during SAG presentation, we have used a panel of murine T cell hybridomas that respond to the bacterial SAG Staphylococcal enterotoxin B (SEB) and to the retroviral SAG Mtv-7 when presented by antigen-presenting cells (APCs) expressing HLA-DR1. Amino acid substitutions of the putative TCR contact residues 59, 64, 66, 77, and 81 on the DR1 beta chain showed that these amino acids are critical for recognition of the SAG SEB by T cells. TCR-MHC class II interactions are thus required for T cell recognit...
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.