Evolution of renin.

New gene data for three aspartyl proteases (human renin, mouse renin and human pepsin) permitted closer analysis of the gene duplication and fusion hypothesis for the evolution of this family of enzymes. Alignment of sequences in the hemilobes of human pepsin revealed only weak homology in amino acid sequences. Nucleotides were, however, more homologous. Splice junctions between putative duplicated exons did not match. Repeated sequences in the human renin gene were detected by hybridization with total human DNA labelled with 32P. These were not, however, consistent with unequal crossing-over between repeated sequences of an ancestral gene having occurred. The data thus provide no immediate support for the gene duplication and fusion hypothesis. The symmetry in structure of an aspartyl protease may arise from the tendency of hydrophilic amino acids to be encoded at splice junctions. This would divide a molecule comprised mainly of beta-sheets into roughly superimposable domains.