A novel conus peptide ligand for K+ channels.
Voltage-gated ion channels determine the membrane excitability of cells. Although many Conus peptides that interact with voltage-gated Na(+) and Ca(2+) channels have been characterized, relatively few have been identified that interact with K(+) channels. We describe a novel Conus peptide that interacts with the Shaker K(+) channel, kappaM-conotoxin RIIIK from Conus radiatus. The peptide was chemically synthesized. Although kappaM-conotoxin RIIIK is structurally similar to the mu-conotoxins that are sodium channel blockers, it does not affect any of the sodium channels tested, but blocks Shaker K(+) channels. Studies using Shaker K(+) channel mutants with single residue substitutions reveal that the peptide interacts with the pore region of the channel. Introduction of a negative charge at residue 427 (K427D) greatly increases the affinity of the toxin, whereas the substitutions at two other residues, Phe(425) and Thr(449), drastically reduced toxin affinity. Based on the Shaker results, a teleost homolog of the Shaker K(+) channel, TSha1 was identified as a kappaM-conotoxin RIIIK target. Binding of kappaM-conotoxin RIIIK is state-dependent, with an IC(50) of 20 nm for the closed state and 60 nm at 0 mV for the open state of TSha1 channels.
Ferber
Michael
M
AG Molekulare und Zelluläre Neuropharmakologie, Max-Planck-Institut für Experimentelle Medizin, Hermann-Rein-Str. 3, D-37075 Göttingen, Germany.
Sporning
Annett
A
Jeserich
Gunnar
G
DeLaCruz
Richard
R
Watkins
Maren
M
Olivera
Baldomero M
BM
Terlau
Heinrich
H
D000595:Amino Acid Sequence; D000818:Animals; D020916:Conotoxins / Q000737:chemistry* / Q000493:pharmacokinetics*; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D005399:Fishes; D020128:Inhibitory Concentration 50; D007700:Kinetics; D008024:Ligands; D008969:Molecular Sequence Data; D008974:Mollusca; D009154:Mutation; D010455:Peptides / Q000737:chemistry; D015221:Potassium Channels / Q000737:chemistry / Q000378:metabolism*; D018075:RNA, Complementary / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012910:Snake Venoms; D014981:Xenopus
D020916:Conotoxins; D018076:DNA, Complementary; D008024:Ligands; D010455:Peptides; D015221:Potassium Channels; D018075:RNA, Complementary; D012910:Snake Venoms; C471553:kappaM-conotoxin RIIIK, Conus radiatus