A regulatory calcium-binding site at the subunit interface of CLC-K kidney chloride channels.

ABSTRACT: The two human CLC Cl(-) channels, ClC-Ka and ClC-Kb, are almost exclusively expressed in kidney and inner ear epithelia. Mutations in the genes coding for ClC-Kb and barttin, an essential CLC-K channel beta subunit, lead to Bartter syndrome. We performed a biophysical analysis of the modulatory effect of extracellular Ca(2+) and H(+) on ClC-Ka and ClC-Kb in Xenopus oocytes. Currents increased with increasing [Ca(2+)](ext) without full saturation up to 50 mM. However, in the absence of Ca(2+), ClC-Ka currents were still 20% of currents in 10 mM [Ca(2+)](ext), demonstrating that Ca(2+) is not strictly essential for opening. Vice versa, ClC-Ka and ClC-Kb were blocked by increasing [H(+)](ext) with a practically complete block at pH 6. Ca(2+) and H(+) act as gating modifiers without changing t

SUBMITTER: Gradogna A 

PROVIDER: S-EPMC2931146 | biostudies-literature | 2010 Sep

REPOSITORIES: biostudies-literature