title: Ethyl bromoacetimidate, a NH2-specific heterobifunctional reagent. Model reactions with ribonuclease.
abstract: Ethyl bromoacetimidate was designed as a potential reagent for cross-linking protein NH2 groups with a vicinal nucleophile. The chemical properties of this compound were studied by model reactions with small molecules. Ethyl bromoacetimidate amidinates lysine residues in ribonuclease at pH 9. In a second step, at lower pH values, one of the bromoacetamidino groups bound to the enzyme alkylates a proximal histidine residue. This substitution is pH-dependent with a sharp optimum at 5.6, the same as was earlier observed for alkylation of histidine-119: histidine-12 by halogenoacetates and halogenoacetamides. A common mechanism is suggested for all these types of alkylation. Ethyl bromoacetimidate thus appears as a short-distance crosslinker which can be used, for example, to explore chemically the microenvironment of an essential lysine residue of an enzyme within the active site.
mesh_terms: D000081:Acetamides / Q000494:pharmacology*; D000818:Animals; D002417:Cattle; D003432:Cross-Linking Reagents; D003488:Cyanogen Bromide; D006863:Hydrogen-Ion Concentration; D007096:Imidoesters; D007700:Kinetics; D010179:Pancreas / Q000201:enzymology; D010446:Peptide Fragments / Q000032:analysis; D011485:Protein Binding; D012260:Ribonucleases / Q000378:metabolism
chemical_list: D000081:Acetamides; D003432:Cross-Linking Reagents; D007096:Imidoesters; D010446:Peptide Fragments; C022006:ethyl bromoacetimidate; D012260:Ribonucleases; D003488:Cyanogen Bromide