The evolution of alpha-fetoprotein and albumin. I. A comparison of the primary amino acid sequences of mammalian alpha-fetoprotein and albumin.

The amino acid sequence of mouse alpha-fetoprotein has been deduced from the nucleotide sequence of its mRNA and three chimeric plasmids containing overlapping segments of its cDNA. A comparison of the amino acid sequence with that of either human and bovine albumin reveals in each case a 32% conservation of primary sequence. In addition, using the regularly spaced positions of cystine bridges, a 2-dimensional structure was generated, which revealed the presence of 3 closely related domains within alpha-fetoprotein. The structures of these domains are identical with the triplicated domains previously observed in several mammalian albumins. These homologies lend strong circumstantial evidence to the proposal that these two proteins arose in evolution as the consequence of a duplication in a common tripartite ancestral gene.