title: C-terminal labelling of beta-casein.
abstract: This paper is the first to report specific labelling of a native protein at its C-terminal end by carboxypeptidase Y-catalyzed transpeptidation between beta-casein and tritiated Phe amide. A tryptic digest of the radiolabelled protein was resolved by reversed-phase HPLC and a single labelled peptide was isolated therefrom. Sequence determination and FAB mass spectrometry showed that the last 2 residues (Val-209, Ile-208) of beta-casein had been deleted and Ile 207 substituted by Phe, deamidation presumably occurring after transpeptidation. Identical results were obtained by transpeptidating the isolated C-terminal tryptic heptapeptide (203-209) of native beta-casein.
mesh_terms: D002268:Carboxypeptidases / Q000378:metabolism; D002364:Caseins / Q000032:analysis / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D007700:Kinetics; D009842:Oligopeptides / Q000378:metabolism; D010649:Phenylalanine / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: D002364:Caseins; D009842:Oligopeptides; D010649:Phenylalanine; C020457:phenylalanine amide; D002268:Carboxypeptidases; C022633:serine carboxypeptidase