title: The isolation, properties and amino acid sequence of erabutoxin c, a minor neurotoxic component of the venom of a sea snake Katicauda semifasciata.
abstract: Erabutoxin c, a minor neurotoxic component of the venom of a sea snake Laticauda semifasciata, was isolated in pure form by repeated column chromatography on CM-cellulose columns. The toxin was crystallizable and monodisperse in rechromatography, disc electrophoresis and isoelectric focusing (isoelectric point, pH9.23-9.25). The molecular weight of the toxin, as estimated by gel filtration, was 7000. The toxin showed the same lethal activity to mice (0.13mug/g body wt., intramuscular injection) and the same effect on isolated frog muscle as erabutoxins a and b, the main toxic components of the venom. The toxin inhibited the acetylcholine contracture but not the potassium chloride contracture of muscle. Erabutoxin c consisted of 62 amino acid residues, containing one fewer lysine and one more histidine than erabutoxin a and one fewer lysine and one more aspartic acid (or asparagine) than erabutoxin b. Erabutoxin c was reduced, S-carboxymethylated and hydrolysed with trypsin. The only fragment different from the corresponding fragments from erabutoxin b was hydrolysed further with pepsin. One of the peptic fragments, which was assumed to have the aspartic acid (or asparagine) residue in question at the C-terminal end, was treated with carboxypeptidase A. The C-terminal residue was found to be an asparagine. It was therefore concluded that erabutoxin c was [51-asparagine]-erabutoxin b.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001216:Asparagine / Q000032:analysis; D002845:Chromatography; D002850:Chromatography, Gel; D004589:Electrophoresis, Disc; D004590:Electrophoresis, Paper; D007525:Isoelectric Focusing; D007928:Lethal Dose 50; D008970:Molecular Weight; D009132:Muscles / Q000187:drug effects; D011506:Proteins / Q000302:isolation & purification; D012911:Snakes; D014688:Venoms / Q000032:analysis* / Q000302:isolation & purification / Q000494:pharmacology / Q000633:toxicity
chemical_list: D011506:Proteins; D014688:Venoms; D001216:Asparagine