Detection and Characterization by High-Performance Liquid Chromatography and Mass Spectrometry of two truncated goat alpha s2-caseins

The identification and characterization of truncated forms of goat alpha(s2)-Cn variants A and E are reported. The two proteins, which have experimental M, values of 24 183 and 24 227 Da, were detected as minor components in a goat milk sample from an autochthonous breed of southern Italy, 'Rossa Mediterranea', by reversed-phase high-performance liquid chromatography/electrospray ionization mass spectrometry (RP-HPLC/ESI-MS). Characterization of the amino acid sequences, performed by coupling trypsin digestion with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), RP-HPLC/ESI-MS and tandem mass spectrometry (MS/MS), demonstrated that the polypeptide chains correspond to the 1-204 sequence of mature alpha(s2)-Cn variant A (component with M, of 24 183 Da) and E (component with M, of 24 227 Da), respectively. These components seem to be the product of a differential splicing of pre-messenger RNA during the translation process of the alpha(s2)-Cn variants A and E.