1K2I

Crystal structure of gamma-chymotrypsin in complex with 7-hydroxycoumarin.

(2001) J Mol Biol 314: 519-525

• PubMed: 11846564 Search on PubMed
• DOI: https://doi.org/10.1006/jmbi.2001.5148
• Primary Citation of Related Structures:  
  1K2I


• PubMed Abstract: 
  

  The 1.8 A crystal structure of 7-hydroxycoumarin (7-HC) bound to chymotrypsin reveals that this inhibitor forms a planar cinnamate acyl-enzyme complex. The phenyl ring of the bound inhibitor forms numerous van der Waals contacts in the S1 pocket of the enzyme, with the p-hydroxyl group donating a hydrogen bond to the main-chain oxygen atom of Ser217, and the o-hydroxyl group forming a water-mediated hydrogen bond with the carbonyl oxygen of Val227. The structure of the acyl-enzyme complex suggests that the mechanism of inhibition of 7-HC involves nucleophilic attack by the Ser195 O(gamma) atom on the carbonyl carbon atom of the inhibitor, accompanied by the breaking of the 2-pyrone ring of the inhibitor, and leading to the formation of a cinnamate acyl-enzyme derivative via a tetrahedral transition state. Comparisons with structures of photoreversible cinnamates bound to chymotrypsin reveal that although 7-HC interacts with the enzyme in a similar fashion, the binding of 7-HC to chymotrypsin takes place in a productive conformation in contrast to the photoreversible cinnamates. In summary, the 7-HC-chymotrypsin complex provides basic insight into the inhibition of chymotrypsin by natural coumarins and provides a structural basis for the design of more potent mechanism-based inhibitors against a wide range of biologically important chymotrypsin-like enzymes.

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Organizational Affiliation: 

International Centre for Chemical Sciences, H. E. J. Research Institute of Chemistry, University of Karachi, Karachi, 75270, Pakistan.