Molecular cloning of mouse mammary gland kappa-casein: comparison with rat kappa-casein and rat and human gamma-fibrinogen.
A cDNA clone for kappa-casein mRNA from the lactating mouse mammary gland was isolated and its nucleotide sequence determined. Analysis of the deduced amino acid sequence revealed a precursor protein with a 21-amino-acid signal sequence and a mature protein of 160 amino acids, the mature mouse protein being 3 amino acids longer than the rat kappa-casein. Northern blot analysis of the lactating rat and mouse mammary gland showed a specific mRNA for rat kappa-casein and two distinct mRNAs for mouse kappa-casein. This result is explained by the presence of two putative polyadenylation sites in mouse kappa-casein cDNA, whereas rat kappa-casein cDNA has only one polyadenylation site. Comparison of the nucleotide sequence and of the deduced amino acid sequence of kappa-casein from mouse with that of the rat showed 85% homology between the two sequences. However, when amino acid sequences of kappa-casein from rat and mouse were compared with ovine kappa-casein, only a 45% homology was observed. Amino acid sequences of kappa-casein from rat, mouse, and sheep were 36.53% homologous with rat and human gamma-fibrinogen. The extent of homology was similar (32%) when nucleotide sequences of corresponding cDNAs were compared. The stretches of homology existing at different regions between the two proteins were more confined toward the amino-terminal half of gamma-fibrinogen. However, when nucleotide sequences were compared, mouse kappa-casein cDNA showed homology only with the second half of the rat gamma-fibrinogen cDNA, i.e., between nucleotides 661-1135. The homology with the human gamma-fibrinogen cDNA spanned over two regions, one between nucleotides 1-328 and the second between nucleotides 591-726.(ABSTRACT TRUNCATED AT 250 WORDS)
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002364:Caseins / Q000235:genetics*; D003001:Cloning, Molecular; D005260:Female; D005340:Fibrinogen / Q000235:genetics*; D006801:Humans; D051379:Mice / Q000235:genetics*; D011061:Poly A / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D012756:Sheep; D014158:Transcription, Genetic
D002364:Caseins; D012333:RNA, Messenger; D011061:Poly A; D005340:Fibrinogen