Functional and structural conservation of CBS domains from CLC chloride channels.
All eukaryotic CLC Cl(-) channel subunits possess a long cytoplasmic carboxy-terminus that contains two so-called CBS (cystathionine beta-synthase) domains. These domains are found in various unrelated proteins from all phylae. The crystal structure of the CBS domains of inosine monophosphate dehydrogenase (IMPDH) is known, but it is not known whether this structure is conserved in CLC channels. Working primarily with ClC-1, we used deletion scanning mutagenesis, coimmunoprecipitation and electrophysiology to demonstrate that its CBS domains interact. The replacement of CBS domains of ClC-1 with the corresponding CBS domains from other CLC channels and even human IMPDH yielded functional channels, indicating a high degree of structural conservation. Based on a homology model of the pair of CBS domains of CLC channels, we identified some residues that, when mutated, affected the common gate which acts on both pores of the dimeric channel. Thus, we propose that the structure of CBS domains from CLC channels is highly conserved and that they play a functional role in the common gate.
Estévez
Raúl
R
Zentrum für Molekulare Neurobiologie Hamburg (ZMNH), Hamburg University, Falkenried 94, D-20246 Hamburg, Germany.
Pusch
Michael
M
Ferrer-Costa
Carles
C
Orozco
Modesto
M
Jentsch
Thomas J
TJ
D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D018118:Chloride Channels / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D003541:Cystathionine beta-Synthase / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D019281:Dimerization; D005260:Female; D047468:Immunoprecipitation; D015640:Ion Channel Gating; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D009865:Oocytes; D018408:Patch-Clamp Techniques; D017434:Protein Structure, Tertiary / Q000502:physiology; D016415:Sequence Alignment; D014981:Xenopus
C086321:CLC-1 channel; D018118:Chloride Channels; D003541:Cystathionine beta-Synthase