Mapping the site of block by tetrodotoxin and saxitoxin of sodium channel II

FEBS Letters

Conti, Franco²  Terlau, Heinrich¹  Stühmer, Walter¹  Imoto, Keiji³  Heinemann, Stefan H.¹  Numa, Shosaku³  Pusch, Michael² 

[1] Max-Planck-Institut für biophysikalische Chemie, D-3400 Göttingen, Germany;Istituto di Cibernetica e Biofisica, I-16146 Genova, Italy;Department of Medical Chemistry and Molecular Genetics, Kyoto University Faculty of Medicine, Kyoto 606, Japan

关键词: Sodium channel;    Site-directed mutagenesis;    cDNA expression;    Tetrodotoxin;    Saxitoxin;    Single-channel conductance;    TTX;    tetrodotoxin;    STX;    saxitoxin;   

DOI  :  10.1016/0014-5793(91)81159-6

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The SS2 and adjacent regions of the 4 internal repeats of sodium channel II were subjected to single mutations involving, mainly, charged amino acid residues. These sodium channel mutants, expressed in Xenopus oocytes by microinjection of cDNA-derived mRNAs, were tested for sensitivity to tetrodotoxin and saxitoxin and for single-channel conductance. The results obtained show that mutations involving 2 clusters of predominantly negatively charged residues, located at equivalent positions in the SS2 segment of the 4 repeats, strongly reduce toxin sensitivity, whereas mutations of adjacent residues exert much smaller or no effects. This suggests that the 2 clusters of residues, probably forming ring structures, take part in the extracellular mouth and/or the pore wall of the sodium channel. This view is further supported by our finding that all mutations reducing net negative charge in these amino acid clusters cause a marked decrease in single-channel conductance.

【 授权许可】

Unknown