The Staphostatin-staphopain complex: a forward binding inhibitor in complex with its target cysteine protease.
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.
Filipek
Renata
R
International Institute of Molecular and Cell Biology, ul Trojdena 4, 02-109 Warsaw, Poland.
Rzychon
Malgorzata
M
Oleksy
Aneta
A
Gruca
Milosz
M
Dubin
Adam
A
Potempa
Jan
J
Bochtler
Matthias
M
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
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