A signature protein-based method to distinguish Mediterranean water buffalo and foreign breed milk

A novel genetic variant at the alpha(s1)-casein locus of water buffalo (WB), 8-residue shorter than its wild-type has been found and sequenced. The internal deletion of the peptide E(35)KVNELsT(42) was confirmed by the isolation of the junction peptide. The 8-residue deletion mutant has a molecular weight that is 919 Da less than that of the wild-type. The novel isoform with a unique f35-42 deletion could be the result of the skipping of exon 6, generating an exon 6-deleted variant of alpha(s1)-casein. The wild-type and its shortened alpha(s1)-casein forms were found to co-exist in many individual milk samples. In contrast, the 8-residue, internally deleted alpha(s1)-casein variant did not occur in water buffaloes of the Mediterranean breed reared in Italy. Wild-type alpha(s1)-casein has 6 to 8 phosphate groups (P) while the internally deleted form 6 and 7P per molecule. (C) 2013 Elsevier Ltd. All rights reserved.