Effect of Enzymic Hydrolysis of the Scissile Bond on the Secondary Structure of a Dimeric Globular Protein

Abstract

ABSTRACT:In order to examine the effect of enzymic cleavage of the reactive site on the secondary structure of the globular protein, Streptomyces subtilisin inhibitor, we studied the thermal denaturation of the moderated inhibitor (the scissile bond cleaved) by means of CD spectroscopy and compared the thermal stability with that of the intact protein. The cleavage gave a significant effect on the thermal stability and lowered the denaturation temperature to 62°C, 20oc below that observed for the intact inhibitor. However, the mechanism of thermal denaturation of the moderated inhibitor was similar to that of the intact one. Based on the hydrophobic and hydrophilic tendency of side chains of amino acid residues, we discuss the effect of hydrolysis at the sciss,ile bond of the protein in the outer flexible region and the a-helix and its neighborhood.