Two of the three genetic variants of goat αs1‐casein which are synthesized at a reduced level have an internal deletion possibly due to altered RNA splicing

Open Access
Publisher Website
Google Scholar
Abstract
This paper describes the elucidation of the primary structure of the three genetic variants of goat αs1-casein, αs1-Cn D, E and F, which have been found to be associated with reduced amounts of αs1-casein in milk. Variant E has the same electrophoretic mobility as variant B, but differs from the latter by the substitutions of Arg for Lys and of Thr for Ala at positions 100 and 195. A genetically controlled event which does not affect the amino acid sequence of this variant might be responsible for its lower rate of synthesis compared to that of αs1-casein B. The deletion of 11 amino acids at positions 59–69 and of 37 amino acids at positions 59–95 in variant B leads to variants D and F. In both cases the deletions, which start at the same position of the polypeptide chain, include the major phosphorylation site of the protein. On the basis of sequence data for casein genes and cDNAs, it was concluded that the deletions occurring in the D and F variants are due to the exclusion of one and several exons, respectively. The observed deletions in the proteins could thus be the consequence of splice site mutations which would induce altered RNA processing and hence reduce the rate of synthesis of the casein.