5-HT3 receptor ion size selectivity is a property of the transmembrane channel, not the cytoplasmic vestibule portals.

ABSTRACT: 5-HT3A receptors select among permeant ions based on size and charge. The membrane-associated (MA) helix lines the portals into the channel's cytoplasmic vestibule in the 4-Å resolution structure of the homologous acetylcholine receptor. 5-HT3A MA helix residues are important determinants of single-channel conductance. It is unknown whether the portals into the cytoplasmic vestibule also determine the size selectivity of permeant ions. We sought to determine whether the portals form the size selectivity filter. Recently, we showed that channels functioned when the entire 5-HT3A M3-M4 loop was replaced by the heptapeptide M3-M4 loop sequence from GLIC, a bacterial Cys-loop neurotransmitter gated ion channel homologue from Gloebacter violaceus. We used homomeric 5-HT3A receptors with either

SUBMITTER: McKinnon NK 

PROVIDER: S-EPMC3182448 | biostudies-literature | 2011 Oct

REPOSITORIES: biostudies-literature