MONOSPECIFICITY OF THE ANTIBODIES TO BOVINE ALPHA(S1)-CASEIN FRAGMENT-140-149 - APPLICATION TO THE DETECTION OF BOVINE-MILK IN CAPRINE DAIRY-PRODUCTS

Comparison of the primary sequences of bovine, ovine and caprine a,, c asein shows a deletion of eight amino acid residues in the ovine casei n region 141-148, which is identical in the bovine and caprine protein s except for a single difference in position 148 (Q or E). Polyclonal antibodies raised in rabbits against the bovine casein sequence 140-14 9 (QELAYTFYPEL) appeared monospecific for bovine alpha(s1)-casein, sin ce no antibody-antigen complex was formed with homologous ovine or cap rine proteins. These antibodies remained unable to recognize the capri ne sequence in the native protein even after extensive tryptic proteol ysis. The lack of immunoreactivity of the antibodies against synthetic caprine alpha(s1)-casein peptide 138-149 (VNQELAYFYPQL) suggested tha t the glutamic acid residue in position 148 is essential for the antig enic character of the bovine peptide. From these observations, the use of these antibodies for the detection and quantitation of bovine milk present in ovine dairy products could be extended to caprine products .