PMID: 12874290 , Related PDB id: 1PXV

Authors:

Filipek R, Rzychon M, Oleksy A, Gruca M, Dubin A, Potempa J, Bochtler M

Title:

The Staphostatin-staphopain complex: a forward binding inhibitor in complex with its target cysteine protease.

Journal:

J Biol Chem. 2003 Oct 17;278(42):40959-66. Epub 2003 Jul 21.

Abstract:

Staphostatins 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.