Complete nucleotide sequence of bovine alpha-lactalbumin gene: comparison with its rat counterpart

The nucleotide sequence of the bovine alpha-lactalbumin gene, whose organization is very similar to that of its rat counterpart, was deduced from the analysis of 2 lambda clones isolated from a HindIII genomic bank. The 3090 sequenced nucleotides comprise 738 bp upstream from the transcription unit (approximately 2 kb) which contains 4 exons of 160, 159, 76 and 330 bp separated by 3 introns of 321, 473 and 504 bp. Comparison with the rat alpha-lactalbumin gene shows similar percentages of homology between the 4 cognate exons. Since only the first three exons are homologous to the corresponding exons of the lysozyme gene, it is suggested that the 4th exons of alpha-lactalbumin and lysozyme genes have different origins. The bovine alpha-lactalbumin mRNA is 725 nucleotides long, excluding the poly(A) tail. The reading frame and the flanking 5' and 3' untranslated regions contain 429, 27 and 269 nucleotides, respectively. The derived amino acid sequence differs at 10 positions from that determined directly on mature alpha-lactalbumin.