Detection and characterization by high‐performance liquid chromatography and mass spectrometry of two truncated goat α s 2 ‐caseins

The identification and characterization of truncated forms of goat α s 2 ‐Cn variants A and E are reported. The two proteins, which have experimental M r 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 α s 2 ‐Cn variant A (component with M r of 24 183 Da) and E (component with M r 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 α s 2 ‐Cn variants A and E. Copyright © 2006 John Wiley & Sons, Ltd.