Site-directed mutagenesis studies of M1-toxin1: Amino acids responsible for toxin-M1 receptor interaction

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)

First Committee Member

Lincoln Potter, Committee Chair


The venom of the green mamba Dendroaspis angusticeps contains several m1-isotoxins with similar amino acid sequences and muscarinic subtype pharmacology. The most prevalent isotoxin, m1-toxin1, has total selectivity for M1 receptors over M2-M5, binds irreversibly to M1 receptors and can bind to M1 receptors occupied with 3H-NMS.There is striking homology between the m1-isotoxins and the remaining 11 muscarinic toxins that bind reversibly to muscarinic receptors. This thesis studied some of the amino acids in m1-toxin1 which are different from those in the reversible toxins. These residues were mutated from the amino acid present in the m1-toxins to the analogous residue in the common muscarinic toxins, and each mutant was examined for its selectivity for M1 receptors, reversibility of binding and allosteric effects.The cDNA for m1-toxin1 was cloned from the venom glands of Dendroaspis angusticeps. The full length cDNA was 514 bp long and included the ubiquitous signal peptide present in all cloned short-chain neurotoxins. The cDNA was expressed in Pichia pastoris and the recombinant toxin behaved as identical to native toxin in binding assays. to M1-M5 receptors.


Biology, Molecular; Health Sciences, Toxicology; Health Sciences, Pharmacology

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