Molecular mechanism of a COOH-terminal gating determinant in the ROMK channel revealed by a Bartter's disease mutation

Thomas P. Flagg, Dana Yoo, Christopher M. Sciortino, Margaret Tate, Michael F. Romero, Paul A. Welling

Research output: Contribution to journalArticle

26 Scopus citations

Abstract

The ROMK subtypes of inward-rectifier K+ channels mediate potassium secretion and regulate NaCl reabsorption in the kidney. Loss-of-function mutations in this pH-sensitive K+ channel cause Bartter's disease, a familial salt wasting nephropathy. One disease-causing mutation truncates the extreme COOH-terminus and induces a closed gating conformation. Here we identify a region within the deleted domain that plays an important role in pH-dependent gating. The domain contains a structural element that functionally interacts with the pH sensor in the cytoplasmic NH2-terminus to set a physiological range of pH sensitivity. Removal of the domain shifts the pKa towards alkaline pH values, causing channel inactivation under physiological conditions. Suppressor mutations within the pH sensor rescued channel gating and trans addition of the cognate peptide restored pH sensitivity. A specific interdomain interaction was revealed in an in vitro protein-protein binding assay between the NH2- and COOH-terminal cytoplasmic domains expressed as bacterial fusion proteins. These results provide new insights into the molecular mechanisms underlying Kir channel regulation and channel gating defects that are associated with Bartter's diseas.

Original languageEnglish (US)
Pages (from-to)351-362
Number of pages12
JournalJournal of Physiology
Volume544
Issue number2
DOIs
StatePublished - Oct 15 2002

ASJC Scopus subject areas

  • Physiology

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