The three-dimensional structure of the papain-leupeptin complex has been determined by X-ray crystallography to a resolution of 2.1 A (overall R-factor = 19.8%). The structure indicates that: (i) leupeptin contacts the S subsites of the papain active site and not the S' subsites; (ii) the 'carbonyl' carbon atom of the inhibitor is covalently bound by the Cys-25 sulphur atom of papain and is tetrahedrally coordinated; (iii) the 'carbonyl' oxygen atom of the inhibitor faces the oxyanion hole and makes hydrogen bond contacts with Gln-19 and Cys-25.
X-ray crystallographic structure of a papain-leupeptin complex.,Schroder E, Phillips C, Garman E, Harlos K, Crawford C FEBS Lett. 1993 Jan 2;315(1):38-42. PMID:8416808
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.