Molecular cloning and sequence analysis of a cDNA for factor V activating enzyme, a coagulant protein from Vipera lebetina snake venom

The complete amino acid sequence of a factor V activator (VLFVA) is deduced from the nucleotide sequence of a cDNA encoding the enzyme. The cDNA was i solated by PCR screening a venomous gland cDNA library of Central Asian Vip era lebetina snake. The full-length cDNA clone, derived from two overlappin g fragments, comprises 1563 basepairs which encode an open reading frame of 259 amino acids. The amino acid sequence of VLFVA (235 amino acids) shows significant homology with snake venom and mammalian serine proteinases. It contains 12 half-cysteines which form, by analogy with other serine protein ases, 6 disulfide bridges. VLFVA has the catalytic triad His43-Asp88-Ser182 . The amino terminal amino acid valine is preceded by 24 amino acids: a put ative signal peptide of 18, mainly hydrophobic, amino acids and an activati ng peptide of 6, mainly hydrophilic amino acid residues. This is the first cloned factor V activating enzyme from snake venom. (C) 1999 Academic Press .