Conservation of chloride channel structure revealed by an inhibitor binding site in ClC-1.
Crystal structures of bacterial CLC proteins were solved recently, but it is unclear to which level of detail they can be extrapolated to mammalian chloride channels. Exploiting the difference in inhibition by 9-anthracene carboxylic acid (9-AC) between ClC-0, -1, and -2, we identified a serine between helices O and P as crucial for 9-AC binding. Mutagenesis based on the crystal structure identified further residues affecting inhibitor binding. They surround a partially hydrophobic pocket close to the chloride binding site that is accessible from the cytoplasm, consistent with the observed intracellular block by 9-AC. Mutations in presumably Cl--coordinating residues yield additional insights into the structure and function of ClC-1. Our work shows that the structure of bacterial CLCs can be extrapolated with fidelity to mammalian Cl- channels.
Estévez
Raúl
R
Zentrum für Molekulare Neurobiologie Hamburg, ZMNH, Universität Hamburg, Falkenried 94, D-20246 Hamburg, Germany.
Schroeder
Björn C
BC
Accardi
Alessio
A
Jentsch
Thomas J
TJ
Pusch
Michael
M
D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D001665:Binding Sites / Q000187:drug effects / Q000235:genetics; D000090007:CLC-2 Chloride Channels; D018118:Chloride Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017124:Conserved Sequence; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed / Q000502:physiology; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques; D017434:Protein Structure, Tertiary; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000378:metabolism; D014981:Xenopus
D000873:Anthracenes; C086321:CLC-1 channel; D000090007:CLC-2 Chloride Channels; D018118:Chloride Channels; D011993:Recombinant Fusion Proteins; D012694:Serine; C010030:9-anthroic acid