Selective tyrosine modification with cyanuric fluoride

Abstract

Among the chemical reagents used for the modification of tyrosine residues in proteins, cyanuric fluoride shows a high degree of selectivity. This is brought out by studies on the reactivity of tyrosines in apomyoglobin, bovine serum albumin, and bovine carbonic anhydrase B. Apomyoglobin was found to contain two cyanuric fluoride reactive and one unreactive residues; the reactive residues are of two types. Bovine serum albumin contains 13 cyanuric fluoride reactive and six unreactive residues; the reactive ones being of two levels of reactivity. Bovine carbonic anhydrase B contains six cyanuric fluoride reactive and two unreactive residues; the reactive ones can be subdivided into three classes of 2 + 2 + 2 residues, according to diminishing reactivity. The results of cyanuration are compared with acetylation with N-acetylimidazole. The criteria of tyrosine residue exposure as revealed by various probes are discussed. The circular dichroism spectra of the three proteins and their derivatives are analyzed.