Rat beta casein cDNA: sequence analysis and evolutionary comparisons

Nucleotide homologies between the glycosylated seed storage proteins ofGlycine max andPhaseolus vulgaris

We have compared the partial nucleotide and derived amino acid sequences of a phaseolin seed storage protein gene ofPhaseolus vulgaris (1) and a conglycinin storage protein gene ofGlycine max (2). Although these proteins are not antigenically related to one another, the architecture of the genes is similar throughout the sequences compared here. Intervening sequences interrupt the same amino acid positions in both genes. Within the 28% of theG. max gene and the 38% of theP. vulgaris gene represented in this comparison, 73% of the nucleotides in the coding and intervening sequences are identical, excluding the insertions and deletions. The nucleotide mismatches found in the coding sequences are distributed throughout the three codon positions with little bias towards the third codon position. In addition to the single nucleotide differences, six insertions or deletions, ranging from three to twenty-seven nucleotides in length, occur in this portion of the coding region and these are partially responsible for the molecular weight differences of the conglycinin α'-subunit and the phaseolin subunit.

Sequence of rat alpha- and gamma-casein mRNAs: evolutionary comparison of the calcium-dependent rat casein multigene family

The complete sequences of rat alpha- and gamma-casein mRNAs have been determined. The 1402-nucleotide alpha- and 864-nucleotide gamma-casein mRNAs both encode 15 amino acid signal peptides and mature proteins of 269 and 164 residues, respectively. Considerable homology between the 5' non-coding regions, and the regions encoding the signal peptides and the phosphorylation sites, in these mRNAs as compared to several other rodent casein mRNAs, was observed. Significant homology was also detected between rat alpha- and bovine alpha s1-casein. Comparison of the rodent and bovine sequences suggests that the caseins evolved at about the time of the appearance of the primitive mammals. This may have occurred by intragenic duplication of a nucleotide sequence encoding a primitive phosphorylation site, -(Ser)n-Glu-Glu-, and intergenic duplication resulting in the small casein multigene family. A unique feature of the rat alpha-casein sequence is an insertion in the coding region containing 10 repeated elements of 18 nucleotides each. This insertion appears to have occurred 7-12 million years ago, just prior to the divergence of rat and mouse.

Nucleotide sequence of cloned cDNA coding for mouse epsilon casein

We isolated cDNA clones, which correspond to the mRNA coding for the smallest of the seven mouse caseins. From the nucleotide sequence of the cDNA we deduced the amino acid sequence of the protein, which we named epsilon casein. Mouse epsilon casein and cow alpha s2 casein show amino acid sequence homologies in the N-terminal region of the mature protein. The signal peptide of mouse epsilon casein shows in length and sequence remarkable homology to the signal peptides of the calcium-precipitable caseins of other species. In accordance with this group of caseins mouse epsilon casein contains in the sequence -Ser-Ser-Glu-Glu- a site for potential multiple phosphorylation.

Construction and identification by partial nucleotide sequence analysis of bovine casein and beta-lactoglobulin cDNA clones

Double stranded (DS) DNA molecules obtained by reverse transcription of a partially purified lactating bovine mammary gland mRNA fraction were cloned into pBR322. Restriction maps for four recombinants were constructed and partial nucleotide sequence analysis of these revealed coding sequences corresponding to alpha s1-, beta-, and kappa-casein and beta-lactoglobulin. The specific single-stranded (SS) cDNAs representing each of these species were identified and their nucleotide lengths estimated. Evidence is presented that these are essentially full-length transcripts of the major mRNA species. On this basis, the cDNA clones range in size from 50% for beta-casein to about 95% for alpha s1-casein in comparison with their respective mRNAs. The DNA sequence spanning all eight phosphoserine residues in alpha s1-casein is presented. These data, together with other serine codon usage data, indicate that the mammary gland phosphoseryl tRNA does not play a role in the incorporation of serine phosphate residues during casein synthesis. The observation that the nucleotide sequences for the serine phosphate cluster in bovine alpha s1-and rat beta-casein exhibit close homology supports the suggestion that these regions have evolved from a common primordial sequence.