title: A high-conductance cation channel from the inner membrane of the free-living soil bacteria Rhizobium etli.
abstract: In this communication we reported the study of a cation channel present in the cytoplasmic membrane of the nitrogen fixing bacterium Rhizobium etli. Inner-membrane (IM) vesicles were purified and fused into planar lipid bilayers (PLBs), under voltage clamp conditions. We have found that fusion of IM-enriched vesicle fractions with these model membranes leads, mainly (>30% of 46 experiments), to the reconstitution of high-conductance channels. Following this strategy, the activity of a channel with main open conductance of 198 pS, in symmetrical 100 mM KCl, was recorded. The single-channel conductance increase to 653 pS in the presence of a 5:1 (cis to trans) gradient of KCl. The channel exhibits voltage dependency and a weak selectivity for cations showing a permeability ratios of P (Rb)/P (K) = 0.96, P (Na)/P (K) = 0.07, and a conductance ratio of gamma(Rb)/gamma(K) = 1.1. The channel here characterized represents a previously undescribed Rhizobium channel although its precise role in rhizobial physiology remains yet to be determined.
authors.affiliation: Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, UNAM, Ap. Postal 510-3, Cuernavaca, Morelos 62210, Mexico. dballeza.uwisc@gmail.com
authors.forename: Daniel
authors.initials: D
authors.lastname: Balleza
authors.forename: Carmen
authors.initials: C
authors.lastname: Quinto
authors.forename: David
authors.initials: D
authors.lastname: Elias
authors.forename: Froylán
authors.initials: F
authors.lastname: Gómez-Lagunas
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D002412:Cations / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D007473:Ion Channels / Q000378:metabolism*; D008051:Lipid Bilayers / Q000378:metabolism; D042163:Rhizobium etli / Q000378:metabolism / Q000502:physiology*; D012988:Soil Microbiology
chemical_list: D001426:Bacterial Proteins; D002412:Cations; D007473:Ion Channels; D008051:Lipid Bilayers