Residues lining the inner pore vestibule of human muscle chloride channels.
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.
Fahlke
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C
Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA. chfahlke@physiology.rwth.aachen.de
Desai
R R
RR
Gillani
N
N
George
A L
AL
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
D018118:Chloride Channels