Martentoxin, a novel K+-channel-blocking peptide: purification, cDNA and genomic cloning, and electrophysiological and pharmacological characterization.
Martentoxin, a novel K+-channel-specific peptide has been purified and characterized from the venom of the East-Asian scorpion (Buthus martensi Karsch). The whole cDNA precursor sequence suggested that martentoxin was composed of 37 residues with a unique sequence compared with other scorpion neurotoxins. The genomic DNA of martentoxin showed an additional intron situated unexpectedly in the 5' UTR region, besides one located close to the C-terminal of the signal peptide. The patch-clamp recording found that martentoxin at the applied dose of 100 nm could strongly block large-conductance Ca2+-activated K+ (BKCa) currents in adrenal medulla chromaffin cells, and BKCa currents blocked by martentoxin could be fully recovered within 30 seconds after washing, which is at least 10 times faster than recovery after charybdotoxin. Meanwhile, a biosensor binding assay showed a fast association rate and a slow dissociation rate of martentoxin binding on rat brain synaptosomes. The binding of martentoxin on rat brain synaptosomes could be inhibited regularly by charybdotoxin, and gradually by toosendanin in a concentration-dependent manner, but not by either apamin or P03 from Buthus martensi. The results thus indicate that martentoxin is a new member in the family of K+-channel-blocking ligands.
Ji
Yong-Hua
YH
Institute of Physiology and Institute of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, China. yhji@server.shcnc.ac.cn
Wang
Wei-Xi
WX
Ye
Jian-Guo
JG
He
Lin-Lin
LL
Li
Ya-Jun
YJ
Yan
Yan-Ping
YP
Zhou
Zhuan
Z
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001667:Binding, Competitive / Q000187:drug effects; D019439:Chromaffin Cells / Q000187:drug effects; D018076:DNA, Complementary / Q000235:genetics / Q000302:isolation & purification; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D015698:Genomic Library; D008969:Molecular Sequence Data; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000737:chemistry* / Q000235:genetics* / Q000494:pharmacology; D010802:Phylogeny; D026902:Potassium Channel Blockers / Q000737:chemistry* / Q000302:isolation & purification / Q000493:pharmacokinetics; D024681:Potassium Channels, Calcium-Activated / Q000187:drug effects; D051381:Rats; D012604:Scorpion Venoms / Q000737:chemistry* / Q000235:genetics* / Q000494:pharmacology; D013574:Synaptosomes / Q000737:chemistry / Q000378:metabolism
D018076:DNA, Complementary; D010455:Peptides; D026902:Potassium Channel Blockers; D024681:Potassium Channels, Calcium-Activated; D012604:Scorpion Venoms; C471035:martentoxin, Buthus martensi