title: Molecular cloning of the major lethal toxins from two kraits (Bungarus flaviceps and Bungarus candidus).
abstract: The major lethal toxins present in the venoms of the red-headed krait, Bungarus flaviceps, and the Malayan krait, Bungarus candidus, have both been purified. Each consists of two polypeptide chains, A and B, joined by a disulfide bond. In the present study, primary structures of these toxins were determined by Edman degradation and by nucleotide sequencing of the cDNA clones. Amino acid sequencing of the N-terminus and enzymatically digested peptides revealed that the A and B chains were highly homologous to those of beta-bungarotoxins (beta-Bgts) from Bungarus multicinctus, respectively. We isolated cDNA clones encoding the A and B chains from both B. flaviceps and B. candidus venom gland cDNA libraries using probes designed based on the cDNA sequence of beta-Bgt from B. multicinctus. Two isoforms of the A chain and one isoform of the B chain were obtained from B. flaviceps, and one isoform of the A chain and two isoforms of the B chain were obtained from B. candidus. Both of the two A chains from B. flaviceps are made up of 119 amino acids and comprise 15 cysteine residues, while the A chains of beta-Bgt from other Bungarus species including B. candidus comprise 13 cysteine residues. The B chains from both species are composed of 59 amino acid residues and comprise seven cysteines. In conclusion, the lethal toxin from B. flaviceps is considered to be a novel isoform of beta-Bgt, which has a different pattern of cysteine residues from known beta-Bgts.
authors.affiliation: Institute of Medicinal Chemistry, Hoshi University, Tokyo 142-8501, Japan.
authors.forename: Ryohei
authors.initials: R
authors.lastname: Yanoshita
authors.forename: Yuko
authors.initials: Y
authors.lastname: Ogawa
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Murayama
authors.forename: Tamotsu
authors.initials: T
authors.lastname: Omori-Satoh
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Saguchi
authors.forename: Shigesada
authors.initials: S
authors.lastname: Higuchi
authors.forename: Orawan
authors.initials: O
authors.lastname: Khow
authors.forename: Lawan
authors.initials: L
authors.lastname: Chanhome
authors.forename: Yuji
authors.initials: Y
authors.lastname: Samejima
authors.forename: Visith
authors.initials: V
authors.lastname: Sitprija
mesh_terms: D000595:Amino Acid Sequence; D002038:Bungarotoxins / Q000737:chemistry / Q000302:isolation & purification / Q000633:toxicity*; D003001:Cloning, Molecular / Q000379:methods*; D018076:DNA, Complementary / Q000302:isolation & purification*; D010802:Phylogeny; D016133:Polymerase Chain Reaction
chemical_list: D002038:Bungarotoxins; D018076:DNA, Complementary