GENETIC DIVERSITY IN SNAKE VENOM THREE-FINGER PROTEINS AND PHOSPHOLIPASE A2 ENZYMES

Abstract

Based on genetic organization and high degree of sequence identity, three-finger protein genes and phospholipase A2 genes appear to represent two multigene families in snake genomes. Unlike intron insertions or deletions, the evolution of protein coding regions of these genes is accelerated by adaptive selection. Thus, the protein coding regions of the two multigene families are more diversified than their intron regions. Alternatively, genetic elements in regulating protein expression were mostly retained during the evolution of the two multigene families. These observations indicate that the multiplicity of the two multigene families expanded on their ancestral gene by gene duplication followed by divergence, and suggest a common route for the evolution of snake toxins.