title: Amino acid sequences of two novel long-chain neurotoxins from the venom of the sea snake Laticauda colubrina.
abstract: From the venom of a population of the sea snake Laticauda colubrina from the Solomon Islands, a neurotoxic component, Laticauda colubrina a (toxin Lc a), was isolated in 16.6% (A280) yield. Similarly, from the venom of a population of L. colubrina from the Philippines, a neurotoxic component, Laticauda colubrina b (toxin Lc b), was obtained in 10.0% (A280) yield. The LD50 values of these toxins were 0.12 microgram/g body wt. on intramuscular injection in mice. Toxins Lc a and Lc b were each composed of molecules containing 69 amino acid residues with eight half-cystine residues. The complete amino acid sequences of these two toxins were elucidated. Toxins Lc a and Lc b are different from each other at five positions of their sequences, namely at positions 31 (Phe/Ser), 32 (Leu/Ile), 33 (Lys/Arg), 50 (Pro/Arg) and 53 (Asp/His) (residues in parentheses give the residues in toxins Lc a and Lc b respectively). Toxins Lc a and Lc b have a novel structure in that they have only four disulphide bridges, although the whole amino acid sequences are homologous to those of other known long-chain neurotoxins. It is remarkable that toxins Lc a and Lc b are not coexistent at the detection error of 6% of the other toxin. Populations of Laticauda colubrina from the Solomon Islands and from the Philippines have either toxin Lc a or toxin Lc b and not both of them.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D055598:Chemical Phenomena; D002621:Chemistry; D004546:Elapid Venoms / Q000032:analysis*; D007928:Lethal Dose 50; D051379:Mice; D008970:Molecular Weight; D009498:Neurotoxins / Q000302:isolation & purification / Q000633:toxicity; D010446:Peptide Fragments / Q000302:isolation & purification; D014357:Trypsin
chemical_list: D004546:Elapid Venoms; D009498:Neurotoxins; D010446:Peptide Fragments; D014357:Trypsin