Crystal Structures of the Staphylococcal Toxin SSL5 in Complex with Sialyl Lewis X Reveal a Conserved Binding Site that Shares Common Features with Viral and Bacterial Sialic Acid Binding Proteins

Baker, Heather M.; Basu, Indira; Chung, Matthew; Caradoc-Davies, Tom T.; Fraser, John D.; Baker, Edward N.

doi:10.1016/j.jmb.2007.09.091

Cited by 61 publications

(71 citation statements)

References 39 publications

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“…Sialyl Lewis X -dependent mechanisms have been described for functional activity of multiple SSL proteins, including SSL5 and SSL11 (27,28). The sialyl Lewis X binding site is fully conserved in SSL3, but its role in TLR2 inhibition has been unclear.…”

Section: Discussionmentioning

confidence: 99%

“…S2A and Table S1) by molecular replacement. SSL3 exhibits the characteristic twodomain fold of superantigens and other SSLs (27,28). The C-terminal β-grasp domain (residues 228-326) contains a V-shaped binding site for sialyl Lewis X , which is conserved in SSL2-6 and -11 ( Fig.…”

Section: Significancementioning

confidence: 99%

“…The C-terminal β-grasp domain (residues 228-326) contains a V-shaped binding site for sialyl Lewis X , which is conserved in SSL2-6 and -11 ( Fig. S3 A and B) (28). The N-terminal OB domain (residues 134-227) displays well-defined but markedly different conformations for loops β1-β2 and α3-β4 (Fig.…”

Section: Significancementioning

confidence: 99%

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Structural basis for inhibition of TLR2 by staphylococcal superantigen-like protein 3 (SSL3)

Koymans

Feitsma

Brondijk

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Toll-like receptors (TLRs) are crucial in innate recognition of invading micro-organisms and their subsequent clearance. Bacteria are not passive bystanders and have evolved complex evasion mechanisms. Staphylococcus aureus secretes a potent TLR2 antagonist, staphylococcal superantigen-like protein 3 (SSL3), which prevents receptor stimulation by pathogen-associated lipopeptides. Here, we present crystal structures of SSL3 and its complex with TLR2. The structure reveals that formation of the specific inhibitory complex is predominantly mediated by hydrophobic contacts between SSL3 and TLR2 and does not involve interaction of TLR2-glycans with the conserved Lewis X binding site of SSL3. In the complex, SSL3 partially covers the entrance to the lipopeptide binding pocket in TLR2, reducing its size by ∼50%. We show that this is sufficient to inhibit binding of agonist Pam 2 CSK 4 effectively, yet allows SSL3 to bind to an already formed TLR2-Pam 2 CSK 4 complex. The binding site of SSL3 overlaps those of TLR2 dimerization partners TLR1 and TLR6 extensively. Combined, our data reveal a robust dual mechanism in which SSL3 interferes with TLR2 activation at two stages: by binding to TLR2, it blocks ligand binding and thus inhibits activation. Second, by interacting with an already formed TLR2-lipopeptide complex, it prevents TLR heterodimerization and downstream signaling.S. aureus | Toll-like receptor | immune evasion | innate immunity | crystal structure

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Section: Discussionmentioning

confidence: 99%

Section: Significancementioning

confidence: 99%

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Structural basis for inhibition of TLR2 by staphylococcal superantigen-like protein 3 (SSL3)

Koymans

Feitsma

Brondijk

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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“…The observation that SSL5 inhibited rolling of neutrophils on immobilized P-selectin suggested impairment of the initial step of neutrophil extravasation toward bacterial infection sites (4). Baker et al analyzed the crystal structure of SSL5 complexed with a sialyl Lewis X tetrasaccharide (sLeX, sialic acid-␣2-3-galactose-␤1-4(fucose-␣1-3)-N-acetylglucosamine), a key determinant of PSGL-1 binding to P-selectin, and demonstrated that sLeX bound to a specific site of the C-terminal domain of SSL5 (3). Because the sialyl-lactosamine unit (sialic acid-␣2-3-galactose-␤1-4-N-acetylglucosamine) is the critical motif for the SSL5/PSGL-1 interaction, SSL5 may recognize other glycoproteins carrying similar carbohydrate chains.…”

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confidence: 99%

Staphylococcal Superantigen-Like Protein 5 Inhibits Matrix Metalloproteinase 9 from Human Neutrophils

et al. 2010

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Staphylococcal superantigen-like proteins (SSLs) constitute a family of exoproteins exhibiting structural similarities to superantigens and enterotoxins but no superantigenic activity. In this article, we present evidence that SSL5 specifically binds to matrix metalloproteinase 9 (MMP-9) and inhibits its enzymatic activity. When human neutrophil cell lysate was applied to recombinant His-tagged SSL5 conjugated to Sepharose, the bound fraction gave a major band of approximately 100 kDa in SDS-polyacrylamide gel electrophoresis. This protein was identified as the proform of MMP-9 (proMMP-9) by peptide mass fingerprinting analysis. The recombinant SSL5-Sepharose also bound to proMMP-9 secreted by interleukin 8 (IL-8)-stimulated neutrophils and HT1080 fibrosarcoma cells. Surface plasmon resonance analysis revealed that recombinant SSL5 bound to proMMP-9 with rather high affinity (dissociation constant [K D ] ‫؍‬ 1.9 nM). Recombinant SSL5 was found to effectively inhibit MMP-9-catalyzed hydrolysis of gelatin and a synthetic fluorogenic peptide in a noncompetitive manner (K i ‫؍‬ 0.097 nM), as assessed by zymography and the fluorescence quenching method. Finally, the transmigration of neutrophils across Matrigel basement membranes in response to N-formyl-methionyl-leucyl-phenylalanine (FMLP) was suppressed by the presence of recombinant SSL5. We discuss possible roles that SSL5 may play in immune evasion of staphylococci by inhibiting MMP and interfering with leukocyte trafficking.

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“…The SSLs are not T cell mitogens like sAgs (15,17,18) but do target components of immunity, including complement (18), the IgA FcR-mediated Ab interaction (19), and glycoproteins expressing the trisaccharide sialyllactosamine (20). A subgroup of SSLs consisting of SSL2, 3,4,5,6, and 11 share a conserved sialyllactosamine binding site (21) allowing targeted binding to a number of different glycoproteins, both on the cell membrane and in plasma. As just one example, SSL11 binds to P-selectin glycoprotein ligand-1 on neutrophils to inhibit P-selectin-mediated attachment that is required for extravasation (3).…”

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confidence: 99%

Specificity of Staphylococcal Superantigen-Like Protein 10 toward the Human IgG1 Fc Domain

Patel

Wines

Langley

et al. 2010

The Journal of Immunology

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Crystal Structures of the Staphylococcal Toxin SSL5 in Complex with Sialyl Lewis X Reveal a Conserved Binding Site that Shares Common Features with Viral and Bacterial Sialic Acid Binding Proteins

Cited by 61 publications

References 39 publications

Structural basis for inhibition of TLR2 by staphylococcal superantigen-like protein 3 (SSL3)

Structural basis for inhibition of TLR2 by staphylococcal superantigen-like protein 3 (SSL3)

Staphylococcal Superantigen-Like Protein 5 Inhibits Matrix Metalloproteinase 9 from Human Neutrophils

Specificity of Staphylococcal Superantigen-Like Protein 10 toward the Human IgG1 Fc Domain

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