Affinity of native kappa-bungarotoxin and site-directed mutants for the muscle nicotinic acetylcholine receptor

Biochemistry. 1994 Nov 8;33(44):12962-7. doi: 10.1021/bi00248a004.


kappa-Bungarotoxin (kappa-bgt) is a 66-residue peptide originally purified from snake venom that acts as an antagonist at certain acetylcholine receptors. It is one of four homologous kappa-neurotoxins that are distinguished from the structurally related alpha-neurotoxins by their ability to block the alpha 3-subunit-containing neuronal nicotinic acetylcholine receptor (nAChR). It has been reported that venom-purified kappa-bgt also displays some affinity for the alpha 1-subunit-containing muscle nAChR to which the alpha-neurotoxins bind with high affinity. Here we report the effects of particular mutations on the ability of recombinant kappa-bgt to block the binding of 125I-alpha-bgt to nAChRs found in fetal mouse muscle and chick skeletal muscle. While the replacement of a proline residue found in all kappa-neurotoxins with an alanine (P-42-A) has relatively little effect, the introduction of a lysine, which is found in 90% of active alpha-neurotoxins at the same position (P-42-K), eliminates muscle receptor affinity at the concentrations tested. In contrast, the replacement of a glutamine in kappa-bgt with a tryptophan found in all active alpha-neurotoxins (Q-32-W) increases the affinity of kappa-bgt for the muscle receptor. When the arginine residue found in all active alpha- and kappa-neurotoxins is replaced by an alanine (R-40-A), the ability of kappa-bgt to block the muscle receptor is reduced to undetectable levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alanine / chemistry
  • Amino Acid Sequence
  • Animals
  • Bungarotoxins / chemistry*
  • Bungarotoxins / genetics
  • Bungarotoxins / metabolism
  • Bungarotoxins / pharmacology
  • Cell Division / drug effects
  • Cell Line
  • Chick Embryo
  • Dose-Response Relationship, Drug
  • Fibroblasts / cytology
  • Fibroblasts / drug effects
  • Fibroblasts / metabolism
  • Glutamine / chemistry
  • Lysine / chemistry
  • Mice
  • Molecular Sequence Data
  • Muscle, Skeletal / embryology
  • Muscle, Skeletal / metabolism
  • Mutagenesis, Site-Directed
  • Proline / chemistry
  • Quail
  • Receptors, Nicotinic / chemistry*
  • Receptors, Nicotinic / drug effects
  • Receptors, Nicotinic / metabolism
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Recombinant Proteins / pharmacology
  • Sequence Homology, Amino Acid
  • Snake Venoms / metabolism
  • Tryptophan / chemistry


  • Bungarotoxins
  • Receptors, Nicotinic
  • Recombinant Proteins
  • Snake Venoms
  • Glutamine
  • Tryptophan
  • Proline
  • Lysine
  • Alanine