Evidence for a function-specific mutation in the neurotoxin, parabutoxin 3.
Parabutoxin 3 (PBTx3), a short-chain alpha-K+ neurotoxin from the scorpion, Parabuthus transvaalicus, is a 37-residue polypeptide cross-linked by three disulphide bridges. The affinity towards Kv1 channels is very weak (Kd approximately 79 micro m for Kv1.1 channels), or moderate (Kd approximately 500 nm for Kv1.2 and Kv1.3 channels). In an effort to generate a more potent K+ channel blocker, we recombinantly produced a mutant PBTx3 by the introduction of an aromatic amino acid, fenylalanine in close proximity of the crucial lysine 26 residue, to create a functional diad similar to subfamily three alpha-K+ toxins. The mutant was tested for his ability to block Kv1.1, Kv1.2 and Kv1.3 channels in Xenopus laevis oocytes: a hundred-fold higher affinity towards Kv1.1 channels and a fivefold increase in affinity towards Kv1.3 channels was observed, when compared to the wild-type toxin. The effect on Kv1.2 channels was similar to the wild-type toxin, indicating a specific interaction site for the mutated residue onto the different Kv-type channels.
Huys
Isabelle
I
Laboratory of Toxicology, University of Leuven, E. Van Evenstraat 4, 3000 Leuven, Belgium.
Tytgat
Jan
J
D000595:Amino Acid Sequence; D000818:Animals; D005260:Female; D051662:Kv1.1 Potassium Channel; D051663:Kv1.2 Potassium Channel; D051664:Kv1.3 Potassium Channel; D008969:Molecular Sequence Data; D009154:Mutation; D009498:Neurotoxins / Q000235:genetics* / Q000494:pharmacology*; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D015221:Potassium Channels / Q000502:physiology; D024642:Potassium Channels, Voltage-Gated; D012604:Scorpion Venoms / Q000235:genetics* / Q000494:pharmacology*; D014982:Xenopus laevis
D051663:Kv1.2 Potassium Channel; D051664:Kv1.3 Potassium Channel; D009498:Neurotoxins; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D012604:Scorpion Venoms; C454815:parabutoxin 3 protein, Parabuthus transvaalicus; D051662:Kv1.1 Potassium Channel