Occurrence of quantitative genetic polymorphism at the caprine beta-CN locus, as determined by a proteomic approach

Abstract

Genetic screening of caseins in caprine milk samples enabled the identification of two novel b-casein (b- CN) phenotypes, C2 and F1, expressed at lower levels (3.3 and 2.7 g L_1 per allele, respectively) than reference b-CN C (4.7 g L_1 per allele), and another lacking in aS-complex. The b-CN C2 and F1 primary structures, determined by MS analysis, corresponded to b-CN C and F, respectively. The reasonable hypothesis supporting the low expression of both variants considers the C2 and F1 alleles as deriving from b-CN C1 and b-CN A1 precursors, respectively, and characterised by a genic transition C/T negatively affecting the mRNA stability. Further, phosphorylation of Thr41 responsible for the 7P b-CN component was determined by a proteomic approach for the first time. Caprine milk containing low levels of antigenic aS1-, aS2- and b-CN can be used for infant formula production and drinking milk for people with cows' milk protein allergy