Interaction of picrotoxin with GABAA receptor channel-lining residues probed in cysteine mutants.
AUTOR(ES)
Xu, M
RESUMO
We used the substituted-cysteine-accessibility method to identify the channel-lining residues in a region (257-261) near the putative cytoplasmic end of the M2 membrane-spanning segment of the rat gamma-aminobutyric acid type A (GABAA) receptor alpha 1 subunit. The residues alpha 1Val257 and alpha 1Thr261 were accessible to charged, sulfhydryl-specific reagents applied extracellularly in both the open and closed states. The accessibility of alpha 1V257C and alpha 1T261C in the closed state implies that the gate must be at least as close to the cytoplasmic end of the channel as alpha 1Val257. Also, the positively charged reagent methanethiosulfonate ethylammonium penetrated from the extracellular end of the channel to alpha 1T261C, with which it reacted, indicating that the anion-selectivity filter is closer to the cytoplasmic end of the channel than this residue is. Co-application of picrotoxin prevented the sulfhydryl reagents from reacting with alpha 1V257C but did not prevent reaction with the more extracellular residue alpha 1T261C. Picrotoxin protection of alpha 1V257C may be due to steric block by picrotoxin bound in the channel at the level of alpha 1Val257; however, if this protection is allosteric, it is not due to the induction of the resting closed state in which alpha 1V257C was accessible to sulfhydryl reagent.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1236419Documentos Relacionados
- Identification of cystic fibrosis transmembrane conductance regulator channel-lining residues in and flanking the M6 membrane-spanning segment.
- Acetylcholine receptor channel structure in the resting, open, and desensitized states probed with the substituted-cysteine-accessibility method
- Hydrophobic packing in T4 lysozyme probed by cavity-filling mutants.
- Adjacent pore-lining residues within sodium channels identified by paired cysteine mutagenesis.
- Soluble receptor-resistant poliovirus mutants identify surface and internal capsid residues that control interaction with the cell receptor.