THE 1.8 ANGSTROMS STRUCTURE OF THE COMPLEX BETWEEN CHYMOSTATIN AND STREPTOMYCES GRISEUS PROTEASE A. A MODEL FOR SERINE PROTEASE CATALYTIC TETRAHEDRAL INTERMEDIATES
The 1.8 A structure of the complex between chymostatin and Streptomyces griseus protease A. A model for serine protease catalytic tetrahedral intermediates.
The naturally occurring serine protease inhibitor, chymostatin, forms a hemiacetal adduct with the catalytic Ser195 residue of Streptomyces griseus protease A. Restrained parameter least-squares refinement of this complex to 1.8 A resolution has produced an R index of 0 X 123 for the 11,755 observed reflections ...
The naturally occurring serine protease inhibitor, chymostatin, forms a hemiacetal adduct with the catalytic Ser195 residue of Streptomyces griseus protease A. Restrained parameter least-squares refinement of this complex to 1.8 A resolution has produced an R index of 0 X 123 for the 11,755 observed reflections. The refined distance of the carbonyl carbon atom of the aldehyde to O gamma of Ser195 is 1 X 62 A. Both the R and S configurations of the hemiacetal occur in equal populations, with the end result resembling the expected configuration for a covalent tetrahedral product intermediate of a true substrate. This study strengthens the concept that serine proteases stabilize a covalent, tetrahedrally co-ordinated species and elaborates those features of the enzyme responsible for this effect. We propose that a major driving force for the hydrolysis of peptide bonds by serine proteases is the non-planar distortion of the scissile bond by the enzyme, which thereby lowers the activation energy barrier to hydrolysis by eliminating the resonance stabilization energy of the peptide bond.
Related Citations:
Structure of the Complex Formed between the Bacterial-Produced Inhibitor Chymostatin and the Serine Enzyme Streptomyces Griseus Protease A Delbaere, L.T.J., Brayer, G.D. (1980) J Mol Biol 139: 45
Organizational Affiliation:
National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi 110067, India jjez@wustl.edu ncbisht@nipgr.ac.in.
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