Structural highlights
FunctionSSPB_STAAU Cysteine protease able to degrade elastin, fibrogen, fibronectin and kininogen. Exhibits a strong preference for substrates where arginine is preceded by a hydrophobic amino acid. Promotes detachment of primary human keratinocytes. Along with other extracellular proteases is involved in colonization and infection of human tissues (By similarity). Publication Abstract from PubMedStaphostatins are the endogenous inhibitors of the major secreted cysteine proteases of Staphylococcus aureus, the staphopains. Our recent crystal structure of staphostatin B has shown that this inhibitor forms a mixed, eight-stranded beta-barrel with statistically significant similarity to lipocalins, but not to cystatins. We now present the 1.8-A crystal structure of staphostatin B in complex with an inactive mutant of its target protease. The complex is held together through extensive interactions and buries a total surface area of 2300 A2. Unexpectedly for a cysteine protease inhibitor, staphostatin B binds to staphopain B in an almost substrate-like manner. The inhibitor polypeptide chain runs through the protease active site cleft in the forward direction, with residues IG-TS in P2 to P2' positions. Both in the free and complexed forms, the P1 glycine residue of the inhibitor is in a main chain conformation only accessible to glycines. Mutations in this residue lead to a loss of affinity of the inhibitor for protease and convert the inhibitor into a substrate. The Staphostatin-staphopain complex: a forward binding inhibitor in complex with its target cysteine protease.,Filipek R, Rzychon M, Oleksy A, Gruca M, Dubin A, Potempa J, Bochtler M J Biol Chem. 2003 Oct 17;278(42):40959-66. Epub 2003 Jul 21. PMID:12874290[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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