title: Residues lining the inner pore vestibule of human muscle chloride channels.
abstract: Chloride channels belonging to the ClC family are ubiquitous and participate in a wide variety of physiological and pathophysiological processes. To define sequence segments in ClC channels that contribute to the formation of their ion conduction pathway, we employed a combination of site-directed mutagenesis, heterologous expression, patch clamp recordings, and chemical modification of the human muscle ClC isoform, hClC-1. We demonstrate that a highly conserved 8-amino acid motif (P3) located in the linker between transmembrane domains D2 and D3 contributes to the formation of a wide pore vestibule facing the cell interior. Similar to a previously defined pore region (P1 region), this segment functionally interacts with the corresponding segment of the contralateral subunit. The use of cysteine-specific reagents of different size revealed marked differences in the diameter of pore-forming regions implying that ClC channels exhibit a pore architecture quite similar to that of certain cation channels, in which a narrow constriction containing major structural determinants of ion selectivity is neighbored by wide vestibules on both sides of the membrane.
authors.affiliation: Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA. chfahlke@physiology.rwth.aachen.de
authors.forename: C
authors.initials: C
authors.lastname: Fahlke
authors.forename: R R
authors.initials: RR
authors.lastname: Desai
authors.forename: N
authors.initials: N
authors.lastname: Gillani
authors.forename: A L
authors.initials: AL
authors.lastname: George
mesh_terms: D000595:Amino Acid Sequence; D018118:Chloride Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D009132:Muscles / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D018408:Patch-Clamp Techniques
chemical_list: D018118:Chloride Channels