Translational efficiency of casein transcripts in Mediterranean river buffalo

Buffalo milk is characterized by the presence of all 4 casein fractions (aS1, b, aS2, and k) encoded by the 4 tightly linked autosomal genes (CSN1S1, CSN2, CSN1S2, and CSN3, respectively). In the present paper, we report for the first time a quantitative characterization of buffalo casein transcripts and show that the 4 genes are not transcribed and translated with the same efficiency. In particular, the analysis of individual milk samples obtained from 9 Mediterranean river buffaloes showed that the most abundant casein fractions were b (53.45%) and aS1 (20.61%), followed by asS2 and k, at 14.28 and 11.66%, respectively. Quantification of the corresponding mRNA showed that the percentage of transcripts of the 4 caseins was 16.48, 23.18, 55.87, and 4.47% for aS1, b, aS2, and k, respectively. Translation efficiency was 0.25 for CSN1S2, 1.31 for CSN1S1, 2.39 for CSN2, and 2.69 for the CSN3 transcripts, respectively. A comparison of nucleotide sequences with the Kozak consensus sequence was also carried out to investigate if the mRNA sequences might be responsible for the observed differences.