5D3D

Crystal structure of Staphylococcal Superantigen-Like protein 3

Summary for 5D3D

• Entry DOI: 10.2210/pdb5d3d/pdb
• Descriptor: Staphylococcal Superantigen-Like protein 3, CHLORIDE ION, THIOCYANATE ION, ... (6 entities in total)
• Functional Keywords: superantigens, superantigen-like proteins, ssl, ssl3, toll-like receptor 2, tlr2, immunology, inflammation, inhibition, immune system
• Biological source: Staphylococcus aureus (strain NCTC 8325)
• Total number of polymer chains: 2
• Total formula weight: 46438.45

Authors

Feitsma, L.J.,Huizinga, E.G. (deposition date: 2015-08-06, release date: 2015-08-19, Last modification date: 2024-05-01)

Primary citation

Koymans, K.J.,Feitsma, L.J.,Brondijk, T.H.,Aerts, P.C.,Lukkien, E.,Lossl, P.,van Kessel, K.P.,de Haas, C.J.,van Strijp, J.A.,Huizinga, E.G.
Structural basis for inhibition of TLR2 by staphylococcal superantigen-like protein 3 (SSL3).
Proc.Natl.Acad.Sci.USA, 112:11018-11023, 2015

PubMed Abstract: 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 Pam2CSK4 effectively, yet allows SSL3 to bind to an already formed TLR2-Pam2CSK4 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.

PubMed: 26283364
DOI: 10.1073/pnas.1502026112

Experimental method

X-RAY DIFFRACTION (1.94 Å)