[Polymorphism of the kappa-casein gene in populations of the subfamily Bovinae].

Polymorphism of the 5'-untranslated region and exon 4 of kappa-casein (kappa-casein) gene was studied in Yakutian and Black Pied cattle, yak, European bison, and buffalo by means of a polymerase chain reaction and subsequent restriction fragment length polymorphism analysis (PCR-RFLP). In the species studied, restriction polymorphism by the endonucleases AluI and Bg/II in the 5'-untranslated region of the gene is absent. Four restriction endonucleases testing nucleotide substitutions in 136 codon (TaqI), 148 codon (HinfI and HindIII), and 167 and 168 codons (PstI) were used to study polymorphism of exon 4. The use of several restriction endonucleases allowed three alleles of kappa-casein (kappa-CnA, kappa-CnB, kappa-CnF) to be typed and new allele variants in yak, European bison, and buffalo to be revealed. Nucleotide sequences of the fragments of exon 4 studied were determined for two new alleles of the gene: kappa-CnG in yak and European bison and kappa-CnH in buffalo. Nucleotide substitutions determining new alleles were localized. In kappa-CnG, 148 and 168 codons coincide with the corresponding codons of kappa-CnB, and 136 and 167 codons correspond to kappa-CnA. Stop codons of kappa-CnG in yak are different from stop codons of other alleles of the gene: TGA, instead of TAA. The nucleotide sequence of exon 4 of kappa-CnH differs from bovine kappa-CnA by 15 nucleotide substitutions, causing 10 amino acid changes in the protein sequence, which coincide with the corresponding known amino acid sequence of kappa-casein in buffalo. Interbreed and interspecies differences in the profile of allele frequencies of the species studied were revealed. Aspects connected with evolution of the alleles of kappa-casein are discussed.