Sequence diversity of Vipera lebetina snake venom,oland serine proteinase homologs - result of alternative-splicing or genome alteration

Four clones encoding homologous protein(ase)s were isolated from the Vipera lebetina (snake) venom,oland cDNA library. One of them represented DNA enc oding factor V activating enzyme (Siigur et al., 1999), the other is homolo gous to VLFVA but has two principal discrepancies in the translated protein sequence in comparison with snake venom serine proteinase structures: in t he active site triad Ser195 is replaced by Asn195 and His57 by Arg57. The t hird and the fourth clone represent combinations of the first two clones. T he possibilities of generation of such clones via trans-splicing of the pri mary gene transcript, by exon shuffling or by unequal crossing-over on the genome level are discussed. (C) 2001 Elsevier Science B.V. All rights reser ved.