Dataset Information

Accelerated evolution of Trimeresurus flavoviridis venom gland phospholipase A2 isozymes.

ABSTRACT: Six Trimeresurus flavoviridis (Habu snake) venom gland phospholipase A2 (PLA2) isozyme genes were found to consist of four exons and three introns and to encode proteins of 138 amino acid residues, including the signal sequence of 16 amino acid residues. Comparison of the nucleotide sequences showed that the introns are much more homologous than the protein-coding regions of exons except for the signal peptide-coding region of the first exon. The numbers of nucleotide substitutions per site (KN) for introns are approximately one-fourth of the numbers of nucleotide substitutions per synonymous site (KS) for the protein-coding regions, indicating that the introns are unusually conserved. The absence of an apparent functional role for the introns suggests that the protein-coding regions, except for the signal peptide-coding domains, have evolved at greater substitution rates than introns. The fact that the numbers of nucleotide substitutions per nonsynonymous site (KA) are close to or larger than KS values for relevant pairs of genes revealed that Darwinian-type accelerated substitutions have occurred in the protein-coding regions or exons. This is compatible with the presence of PLA2 species with diverse physiological activities in the venom.

SUBMITTER: Nakashima K

PROVIDER: S-EPMC46847 | biostudies-other | 1993 Jul

REPOSITORIES: biostudies-other

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Accelerated evolution of Trimeresurus flavoviridis venom gland phospholipase A2 isozymes.

Nakashima K K Ogawa T T Oda N N Hattori M M Sakaki Y Y Kihara H H Ohno M M

Proceedings of the National Academy of Sciences of the United States of America 19930701 13

Six Trimeresurus flavoviridis (Habu snake) venom gland phospholipase A2 (PLA2) isozyme genes were found to consist of four exons and three introns and to encode proteins of 138 amino acid residues, including the signal sequence of 16 amino acid residues. Comparison of the nucleotide sequences showed that the introns are much more homologous than the protein-coding regions of exons except for the signal peptide-coding region of the first exon. The numbers of nucleotide substitutions per site (KN) ...[more]

PMID: 8327468

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Project description:Conventional chromatographic analysis showed that phospholipase A(2) (PLA(2)) isoenzymes of the venom of Trimeresurus flavoviridis (Habu snake) of Okinawa island are profoundly different in composition from those of T. flavoviridis of Amami-Oshima and Tokunoshima islands. The most striking feature was that myotoxic [Lys(49)]PLA(2) isoenzymes, called BPI and BPII, which are expressed abundantly in the venoms of Amami-Oshima and Tokunoshima T. flavoviridis, are missing from the venom of Okinawa T. flavoviridis. Northern blot analysis of Okinawa T. flavoviridis venom-gland mRNA species showed the absence of BPI and BPII mRNA species. Analysis by single-stranded conformational polymorphism-PCR of venom-gland mRNA species of T. flavoviridis from three islands, with reference to five DNA species each encoding different PLA(2) isoenzymes from Tokunoshima T. flavoviridis venom gland, also suggested that BPI and BPII mRNA species are not expressed in Okinawa T. flavoviridis venom gland. In contrast, genomic Southern blot analysis with a variety of probes showed that only the bands corresponding to the upstream and downstream regions of the genes for BPI and/or BPII can be detected in Okinawa T. flavoviridis. These results suggested that the genes for BPI and BPII in Okinawa T. flavoviridis genome had been inactivated to form pseudogenes. Differently from Amami-Oshima and Tokunoshima T. flavovirdis genomic DNAs, PCR amplification of the segments of BPI and BPII genes between the 5' moiety of second exon and the middle portion of second intron failed for Okinawa T. flavoviridis genomic DNAs. In sequence analysis of the two segments involving polymorphism between BPI and BPII genes, which are located in first exon and third exon, respectively, only one base was detected at the polymorphic positions for pseudogene in Okinawa T. flavoviridis genome. Based on these facts, it became evident for pseudogene that the upstream region of BPI gene down to the 5' moiety of second exon and the downstream region of BPII gene starting from the middle portion of second intron are in a linked form with a possible insertion. Such observations suggest that venom-gland genes for PLA(2) isoenzymes in T. flavoviridis snakes isolated for one to two million years have evolved independently. Their evolution is regional and seems, from several lines of consideration and observation, to be adaptive to the environment.

Dataset Information

Accelerated evolution of Trimeresurus flavoviridis venom gland phospholipase A2 isozymes.

Publications

Accelerated evolution of Trimeresurus flavoviridis venom gland phospholipase A2 isozymes.

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