cd04591: CBS_pair_EriC_assoc_euk_bac (this model, PSSM-Id:239964 is obsolete and has been replaced by 341367)
This cd contains two tandem repeats of the cystathionine beta-synthase (CBS pair) domains in the EriC CIC-type chloride channels in eukaryotes and bacteria. These ion channels are proteins with a seemingly simple task of allowing the passive flow of chloride ions across biological membranes. CIC-type chloride channels come from all kingdoms of life, have several gene families, and can be gated by voltage. The members of the CIC-type chloride channel are double-barreled: two proteins forming homodimers at a broad interface formed by four helices from each protein. The two pores are not found at this interface, but are completely contained within each subunit, as deduced from the mutational analyses, unlike many other channels, in which four or five identical or structurally related subunits jointly form one pore. CBS is a small domain originally identified in cystathionine beta-synthase and subsequently found in a wide range of different proteins. CBS domains usually come in tandem repeats, which associate to form a so-called Bateman domain or a CBS pair which is reflected in this model. The interface between the two CBS domains forms a cleft that is a potential ligand binding site. The CBS pair coexists with a variety of other functional domains. It has been proposed that the CBS domain may play a regulatory role, although its exact function is unknown. Mutations of conserved residues within this domain in CLC chloride channel family members have been associated with classic Bartter syndrome, Osteopetrosis, Dent's disease, idiopathic generalized epilepsy, and myotonia.