Expanding the scorpion toxin alpha-KTX 15 family with AmmTX3 from Androctonus mauretanicus.
A novel toxin, AmmTX3 (3823.5 Da), was isolated from the venom of the scorpion Androctonus mauretanicus. It showed 94% sequence homology with Aa1 from Androctonus australis and 91% with BmTX3 from Buthus martensi which, respectively, block A-type K+ current in cerebellum granular cells and striatum cultured neurons. Binding and displacement experiments using rat brain synaptosomes showed that AmmTX3 and Aa1 competed effectively with 125I-labelled sBmTX3 binding. They fully inhibited the 125I-labelled sBmTX3 binding (Ki values of 19.5 pm and 44.2 pm, respectively), demonstrating unambiguously that the three molecules shared the same target in rat brain. The specific binding parameters of 125I-labelled AmmTX3 for its site were determined at equilibrium (Kd = 66 pm, Bmax = 22 fmol per mg of protein). Finally, patch-clamp experiments on striatal neurons in culture demonstrated that AmmTX3 was able to inhibit the A-type K+ current (Ki = 131 nm).
Vacher
Hélène
H
UMR 6560 CNRS and UMR 6150 CNRS, Université de la Méditerranée, Faculté de Médecine secteur Nord, IFR Jean Roche, Marseille, France.
Alami
Meriem
M
Crest
Marcel
M
Possani
Lourival D
LD
Bougis
Pierre E
PE
Martin-Eauclaire
Marie-France
MF
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D007700:Kinetics; D008297:Male; D013058:Mass Spectrometry; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D009474:Neurons / Q000166:cytology; D009479:Neuropeptides / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley; D012604:Scorpion Venoms / Q000378:metabolism*; D012605:Scorpions / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013997:Time Factors
D000596:Amino Acids; C471416:AmmTX3 protein, Androctonus mauretanicus; D009479:Neuropeptides; D012604:Scorpion Venoms; C098736:Tx3 neurotoxin; D011188:Potassium