PMID: 15357669

Authors:

Janowski R, Kozak M, Jankowska E, Grzonka Z, Jaskolski M

Title:

Two polymorphs of a covalent complex between papain and a diazomethylketone inhibitor.

Journal:

J Pept Res. 2004 Oct;64(4):141-50.

Abstract:

The three-dimensional structure of two polymorphs of a ZLFG-CH2-papain covalent complex has been determined by X-ray crystallography. The structures indicate that: (i) the methylene carbon atom of the inhibitor is covalently bound to the Sgamma atom of Cys25 of papain; (ii) the hydrophobic S2 pocket formed by Pro68, Val133, Val157, and Asp158 is occupied by the inhibitor's phenylalanyl P2 side chain; (iii) extensive hydrogen bonding and hydrophobic interactions are responsible for the interaction of the inhibitor with the enzyme. Comparison with similar structures suggests that in covalent complexes preservation of main chain-main chain interactions between the enzyme and the inhibitor may have higher priority than the P-S interactions.