PEPTIDE BIOTINYLATION WITH AMINE-REACTIVE ESTERS - DIFFERENTIAL SIDE-CHAIN REACTIVITY

N-hydroxysuccinimide (NHS) esters of biotin are reported to react spec ifically with amino groups of peptides and proteins. However, we have found that these reagents can readily acylate other functional groups in specific peptide sequences under relatively mild conditions. We hav e extended our inquiry of sequence-dependent acylation by evaluating t he reactivity of a variety of commonly employed biotinylation reagents typically used for amino group modification. These included the p-nit rophenyl ester of biotin, NHS-esters of biotin containing aminohexanoi c acid spacer arms, and a sulfonated NHS-biotin ester that contained a disulfide bond within its spacer. The decapeptide [D-Lys(6)]gonadotro pin releasing hormone was employed as a model peptide. Reaction produc ts were characterized by high-performance liquid chromatography, amino acid compositional analysis, reaction with hydroxylamine, and mass sp ectrometry. In addition to the O-acylation of Ser(4) and Tyr(5) in thi s peptide, we have also identified a novel biotinylation of the Arg(8) side chain. (C) 1997 Elsevier Science Inc.