Structural highlights
Publication Abstract from PubMedStaphylococcus aureus is a prevalent and significant human pathogen. Among the repertoire of virulence factors produced by this bacterium are the 14 Staphylococcal superantigen-like (SSL) proteins. SSL4 is one member of this family and contains a highly conserved carbohydrate binding site also found in SSL2, SSL3, SSL5, SSL6, and SSL11. Recombinant SSL4(t), comprising amino acids 109-309 of SSL4-Newman, is shown to bind and be internalised by human granulocytes and macrophages in a sialic acid (Sia) dependent manner. SSL4(t) can compete with itself for cell binding, indicating that binding is target specific. A 2.5A resolution crystal structure of SSL4(t) complexed with sialyl Lewis-X (sLe(x) - Neu5Acalpha2-3Galbeta1-4(Fucalpha1-3)GlcNAc) revealed a similar binding site to SSL5 and SSL11. These data, along with data on SSL4(t) binding to a glycan array and biosensor analysis of sLe(x) and sLacNac binding are compared with SSL11. Although these proteins show great similarity in their carbohydrate binding sites with a root mean square (rms) difference between main chain atom positions of only 0.34A, these proteins differ in detail in their affinity for sLe(x) and sLacNac, as well as their glycan preference. Together with cell binding data this shows how S. aureus produces multiple related proteins that target myeloid cells through specific sialyllactosamine containing glycoproteins. The Structural and Functional Properties of Staphylococcal Superantigen-Like 4 (SSL4).,Hermans SJ, Baker HM, Sequeira RP, Langley RJ, Baker EN, Fraser JD Infect Immun. 2012 Sep 4. PMID:22949551[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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