PROTEIN CLEAVAGE BY TRANSITION-METAL COMPLEXES BEARING AMINO-ACID SUBSTITUENTS

In this report, we describe protein damage by a series of metal comple xes that mediate the formation of hydroxyl radical. The protein target s used are bovine serum albumin (BSA) and carboxypeptidase A (CPA). BS A contains several electrostatic, hydrogen bonding and hydrophobic bin ding sites for potential interaction with the metal complexes, and CPA contains a specific phenylalanine binding site. The data presented in this study show that aromatic side chain damage and backbone cleavage occur to similar extents with all the complexes. Reasonable levels of backbone cleavage specificity can be attained with relatively few rec ognition elements, despite the fact that a diffusible radical mediates cleavage. Incorporation of additional recognition elements can enlarg e the set of cleavage sites. We show that the chemical environment of the cleavage reaction, manipulated by using different buffers, can dra matically affect the outcome of the cleavage reaction. Our work sugges ts that backbone cleavage site is determined by three factors: the bin ding sites of the metal complexes, the role of reactive sites on the p rotein backbone, and the influence of the chemical environment on the reaction. (C) 1998 Elsevier Science B.V. All rights reserved.