Three Trimeresurus okinavensis (To; himehabu snake, Crotalinae) venom gland phospholipase A(2) (PLA(2)) isozyme-encoding genes, gPLA(2)-o1, gPLA(2)-o(2) and gPLA(2)-o3, were isolated from its genomic DNA library. The nucleotide (nt) sequence analysis revealed that two of the three genes (gPLA(2)-o2 and gPLA(2)-o3) occasionally have been converted to inactivated genes by introduction of one base insertion or substitution. It was confirmed from Southern blot analysis that the To haploid genome contains only three venom gland PLA(2) isozyme genes herein isolated. Comparison of these genes showed that nonsynonymous nt substitutions have occurred more frequently than synonymous nt substitutions in the protein-coding regions, except for the signal-peptide coding domain, implying that To venom gland PLA(2) isozyme genes have evolved via accelerated evolution, Such an evolutionary feature of To venom gland PLA(2) isozyme genes proves the general universality of accelerated evolution previously drawn for venom gland PLA(2) isozyme genes of other crotalinae snakes. The variability in the mature protein-coding regions of three To venom gland PLA(2) isozyme genes appears to have been brought about by natural selection for point mutations.
