Regional and accelerated molecular evolution in group I snake venom gland phospholipase A(2) isozymes

In accordance with detection of a few phospholipase A(2) (PLA(2)) isozyme g enes by Southern blot analysis, only two cDNAs, named NnkPLA-I and NnkPLA-I I, encoding group I PLA(2)s, NnkPLA-I and NnkPLA-II, respectively, were iso lated from the venom gland cDNA library of Elapinae Naja naja kaouthia of M alaysia. NnkPLA-I and NnkPLA-II showed four amino acid substitutions, all o f which were brought about by single nucleotide substitution. No existence of clones encoding CM-II and CM-III, PLA(2) isozymes which had been isolate d from the venom of N. naja kaouthia of Thailand, in Malaysian N. naja kaou thia venom gland cDNA library was verified by dot blot hybridization analys is with particular probes. NnkPLA-I and NnkPLA-II differed from CM-II and C M-III with four and two amino acid substitutions. respectively, suggesting that their molecular evolution is regional. The comparison of NnkPLA-I, Nnk PLA-II and cDNAs encoding other group I snake venom gland PLA(2)s indicated that the 5'- and 3'-untranslated regions are more conserved than the matur e protein-coding region and that the number of nucleotide substitutions per nonsynonymous site is almost equal to that per synonymous sire in the prot ein-coding region, suggesting that accelerated evolution has occurred in gr oup I venom gland PLA(2)s possibly to acquire new physiological functions. (C) 1999 Elsevier Science Ltd. All rights reserved.