title: The Staphostatin-staphopain complex: a forward binding inhibitor in complex with its target cysteine protease.
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.
authors.affiliation: International Institute of Molecular and Cell Biology, ul Trojdena 4, 02-109 Warsaw, Poland.
authors.forename: Renata
authors.initials: R
authors.lastname: Filipek
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Rzychon
authors.forename: Aneta
authors.initials: A
authors.lastname: Oleksy
authors.forename: Milosz
authors.initials: M
authors.lastname: Gruca
authors.forename: Adam
authors.initials: A
authors.lastname: Dubin
authors.forename: Jan
authors.initials: J
authors.lastname: Potempa
authors.forename: Matthias
authors.initials: M
authors.lastname: Bochtler
mesh_terms: D001426:Bacterial Proteins; D002352:Carrier Proteins / Q000737:chemistry* / Q000494:pharmacology; D003546:Cysteine Endopeptidases / Q000737:chemistry* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D008958:Models, Molecular; D009154:Mutation; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013997:Time Factors
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D010455:Peptides; C479136:staphostatin B protein, Staphylococcus aureus; D003546:Cysteine Endopeptidases; C479137:staphopain B protein, Staphylococcus aureus