Structure-Function Relationship of Hydrophiidae Postsynaptic Neurotoxins
Final rept. 1 Mar 1989-28 Feb 1992
COLORADO STATE UNIV FORT COLLINS DEPT OF BIOCHEMISTRY
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Lapemis toxin, from a Hydrophiidae sea snake venom Lapemis hardwickii, binds tightly and specifically to the nicotinic acetylcholine receptor AChR inhibiting neumuscular transmission and results in muscular paralysis. In order to study the structure-function relationship of Lapemis toxin structural loop domains were synthesized. The domain peptide were found to be non-toxic at 8 mgkg dosage i.v., mice or 114 times the known LD50 of Lapemis toxin. Binding studies with Torpedo californica acetylcholine receptor and 125-I radiolabelled toxin and peptides indicated that Lapemis toxin and peptide Bl bound with equilibrium dissociation constants of 2 nM and 40 nM, respectively. The other peptides had no detectable binding. Chemical modification study of which of the three arginines, located in the central loop, are involved in the neurotoxin-AChR demonstrated that Arg-31 and Arg-34 residues are involved in toxin-AChR interaction. The central loop B with intact disulfide bond of the native lapemis toxin appears to play a dominate role in the toxins binding ability to the receptor. Characterization of the 9 kD and the 13.5 kD proteins fractionated from Lapemis hardwickii venom have been identified from partial sequence data as parvalbumin and phospholipase A2, respectively.
- Anatomy and Physiology