Correlations between heterozygosity and evolutionary rate of proteins

Abstract

Amino acid sequence analysis and electrophoretic analysis of protein variation have been widely used for measuring genetic differentiation between diverging lines of descent. The problem of identifying the causes of protein evolution and divergence is, however, largely unsolved. Using data extracted from a collection of allozyme surveys of vertebrate species, we report here that protein heterozygosity is correlated with both protein genetic distance and protein amino acid substitution rate. Proteins with high heterozygosity are shown to have evolved at a faster rate than proteins with low heterozygosity. Evolutionary rate estimates obtained from the two techniques of amino acid sequencing and electrophoretic analysis are highly correlated over those proteins assayed by both methods. The observed relationship between protein heterozygosity and genetic distance cannot be completely accounted for by neutral theory, but suggests that a substantial proportion of genetic distance accumulated between species is the result of selective substitution.