Bovine serum albumin as a catalyst: VI. Specificity of several nucleophilic groups in the protein for N-dansylaziridine

Abstract

The reaction of N-dansylaziridine with serum albumin (both bovine and human) results in incorporation of about 3 mol of covalently bound dansyl label per mol protein. This indicates that a number of nucleophilic groups in these proteins (in addition to the free sulfhydryl group) will react with this reagent. The reaction has been studied in detail for bovine serum albumin and the results suggest that one of the sites labelled by the reagent may be at the unusual “catalytic site” responsible for the enzyme-like activity of bovine serum albumin recently described (Taylor, R.P., Chau, V., Bryner C. and Berga S. (1975) J. Am. Chem. Soc. 97, 1934–1942). The reaction of N-dansylaziridine with a variety of other proteins indicates a pattern of labelling consistent with high specificity for the sulfhydryl group. The explanation for the unexpected excess reactivity of albumin with the “sulfhydryl specific” reagent N-dansylaziridine must be related to the three-dimensional structure in albumin which enables a number of specific residues to manifest unusually high degrees of nucleophilic reactivity.