Author/Editor		Kordiš, Dušan; Gubenšek, Franc
Title		Ammodytoxin C gene helps to elucidate the irregular structure of Crotalinae group II phospholipase A2 genes
Type		članek
Source		Eur J Biochem
Vol. and No.		Letnik 240
Publication year		1996
Volume		str. 83-90
Language		eng
Abstract		Ammodytoxin C is a presynaptically neurotoxic phospholipase A2 (PLA2) expressed in the venom glands of Vipera ammodytes (subfamily Viperinae). The gene spans more than 4 kb and consist of five exons and four introns characteristic og roup II phospholipase A2 genes. The first exon encodes the 5' untransled region, the second exon encodes most of the signal peptide, while exons 3-5 encode three parts of the mature protein. Comparison of the Crotalinae and Viperinae PLA2 genes has shown that Crotalinae PLA2 retain the first intron in their mRNAs. The apparent cause of this retention is a deletion of 40 bp in the first exon of PLA2 genos of the subfamily Crotalinae, which prevents splicing of the first intron. Analtsis of the secondary structure of the pre-mRNA of the ammodytoxin C gene has shown that the first exon is able to form an intra-exon hairpin which is absent in Crotalinae PLA2 pre-mRNAs. Our results indicate that this intra-exon hairpin structure is essential for the splicing of the retained first intron. Contrary to the prdictions of the neutral theory of molecular evolution, the introns of all known snake venom PLA2 genes are conserved up to 90%, that is considerably more than the exons. Consequently it is proposed that highly conserved introns, inmultigene families, which evolve under positive Darwinian selction, may have an important role in enabling homologous recombination.
Descriptors		PHOSPHOLIPASES A VIPER VENOMS CROTALID VENOMS RATS AMINO ACID SEQUENCE BASE SEQUENCE EXONS INTRONS MOLECULAR SEQUENCE DATA NUCLEIC ACID CONFORMATION RNA PRECURSORS RNA SPLICING SEQUENCE HOMOLOGY, NUCLEIC ACID SNAKES VIPERIDAE