Proteomic characterisation and phylogenetic derivation of ovine alpha-s1-CN B and alpha-s1-CN G genetics variants

A combination of chromatographic, immunoelectrophoretic and mass spectrometric methods was applied to healthy individual milk of ovine massese breed. Caseome of alpha-s1-casein (alpha-s1-CN) fraction was characterised in homozygous and heterozygous phenotypes for the novel B and G genetic variants. Using ovine alpha-s1-CN C counterpart as reference, amino acid substitutions and phosphorylated components were determined. The replacement of p.Arg90>His and p.Ile194>Thr were found in alpha-s1-CN B variant, while the single p.Ile194>Thr substitution occurred in alpha-s1-CN G variant. The quali-quantitative composition of phosphorylated alpha-s1-CN components in milk of animals bearing each variant was defined, highlighting possible genetic markers for assessment of dairy product quality. The heterogeneity of the electrophoretic profiles of the corresponding caseomes was due to the number of phosphorylated components and their net charge and pI values, and updated the ovine alpha-s1-CN phylogenetic tree, suggesting alpha-s1-CN G as the ancestral variant of alpha-s1-CN B and other variants