title: Chemical modification of cationic residues in toxin a from king cobra (Ophiophagus hannah) venom.
abstract: The cationic groups of arginine and lysine residues in alpha-neurotoxin, Toxin a, isolated from king cobra (Ophiophagus hannah) venom were subjected to modification with trinitrobenzene sulfonate (TNBS) and p-hydroxyphenylglyoxal (HPG), respectively. The trinitrophenylated (TNP) derivatives of Toxin a at Lys-10, 56, or 71 showed approximately 25% residual lethality, and modifications on Lys-10 and 56 or Lys-10 and 50 resulted in a decrease of lethality by 84% and 86%, respectively. Modifications on Arg-34, 37, and 70 and Arg-34, 37, and 72 in Toxin a caused a decrease in lethality by 92% and 93%, respectively, and it almost completely lost its lethality and binding activity to nicotinic acetylcholine receptor (nAChR) when all four arginine residues were modified. These results indicate that in addition to the cationic residues on loop II (Arg-34, 37), loop III (Lys-50, 56), and the C-terminal tail (Arg-70, 72; Lys-71), Lys-10 on loop I is also related to the neurotoxicity of Toxin a.
authors.affiliation: School of Chemistry, Kaohsiung Medical College, Taiwan, ROC.
authors.forename: S R
authors.initials: SR
authors.lastname: Lin
authors.forename: S H
authors.initials: SH
authors.lastname: Chi
authors.forename: L S
authors.initials: LS
authors.lastname: Chang
authors.forename: K W
authors.initials: KW
authors.lastname: Kuo
authors.forename: C C
authors.initials: CC
authors.lastname: Chang
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001120:Arginine / Q000378:metabolism; D001665:Binding Sites; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D003039:Cobra Neurotoxin Proteins / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D005260:Female; D008239:Lysine / Q000378:metabolism; D008297:Male; D051379:Mice; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D010658:Phenylglyoxal / Q000031:analogs & derivatives / Q000494:pharmacology; D011978:Receptors, Nicotinic / Q000378:metabolism; D017421:Sequence Analysis; D018675:Toxicity Tests; D014302:Trinitrobenzenesulfonic Acid / Q000494:pharmacology; D014357:Trypsin / Q000378:metabolism
chemical_list: D000596:Amino Acids; D003039:Cobra Neurotoxin Proteins; D010446:Peptide Fragments; D011978:Receptors, Nicotinic; C028465:4-hydroxyphenylglyoxal; C025154:alpha-cobratoxin; D014302:Trinitrobenzenesulfonic Acid; D001120:Arginine; D014357:Trypsin; D008239:Lysine; D010658:Phenylglyoxal