The chemotaxis inhibitory protein, CHIPS, is an excreted virulence factor which acts by binding to C5a and formylated peptide receptor (FPR), blocking phagocyte responses. A fragment of CHIPS, which contains residues 31-121 comprises of an alpha helix packed onto a four stranded anti-parallel beta-sheet. Most of the conserved residues of CHIPS are present in the alpha-helix [1].

1: The structure of the C5a receptor-blocking domain of chemotaxis inhibitory protein of Staphylococcus aureus is related to a group of immune evasive molecules. Haas PJ, de Haas CJ, Poppelier MJ, van Kessel KP, van Strijp JA, Dijkstra K, Scheek RM, Fan H, Kruijtzer JA, Liskamp RM, Kemmink J; J Mol Biol. 2005;353:859-872. PMID:16213522