The inward rectifying potassium (Kir) channel family consists of several potassium channels that play a central role in many cell types. These channels are notable for a unique cytoplasmic domain containing putative binding sites for regulatory ligands such as protons and membrane phospholipids. Mutations that alter responsiveness to these ligands can result in disease, e.g. Bartter's syndrome secondary to mutations in Kir1.1 that alter sensitivity to either pH or to phosphatidylinositol bisphosphate (PIP2), resulting in decreased channel activity and derangement of salt transport/excretion in the kidney. Recently, the crystal structure of one member of the prokaryotic protein family, KirBad.1, with significant primary sequence similarities with eukaryotic Kirs, was solved. We have shown that purified KirBad.1 reconstituted in liposomes is a potassium selective channel, regulated by protons and PIP2 with functional characteristics similar to eukaryotic Kirs. The unique ability to examine a pure protein preparation in a fully defined milieu, in combination with the crystal structure, provides a valuable tool in elucidating the structural mechanisms of ligand gating. The overall goal of this proposal is to define structural mechanisms of KirBac1.1 proton and phospholipid gating, using electrophysiological and liposomal assays. Results from this proposal will provide insight into proton and PIP2 gating mechanisms of Kir channels in general, and may lead to therapy of diseases caused by altered ligand regulation of Kir function, such as Bartter's syndrome.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Cellular and Molecular Biology of the Kidney Study Section (CMBK)
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Ketchum, Christian J
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Saint Louis University
Schools of Medicine
Saint Louis
United States
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Wang, Shizhen; Lee, Sun-Joo; Heyman, Sarah et al. (2012) Structural rearrangements underlying ligand-gating in Kir channels. Nat Commun 3:617
D'Avanzo, Nazzareno; Hyrc, Krzysztof; Enkvetchakul, Decha et al. (2011) Enantioselective protein-sterol interactions mediate regulation of both prokaryotic and eukaryotic inward rectifier K+ channels by cholesterol. PLoS One 6:e19393
Singh, Dev K; Shentu, Tzu-Pin; Enkvetchakul, Decha et al. (2011) Cholesterol regulates prokaryotic Kir channel by direct binding to channel protein. Biochim Biophys Acta 1808:2527-33
Paynter, Jennifer J; Andres-Enguix, Isabelle; Fowler, Philip W et al. (2010) Functional complementation and genetic deletion studies of KirBac channels: activatory mutations highlight gating-sensitive domains. J Biol Chem 285:40754-61
Wang, Shizhen; Alimi, Yewande; Tong, Ailing et al. (2009) Differential roles of blocking ions in KirBac1.1 tetramer stability. J Biol Chem 284:2854-60
Singh, Dev K; Rosenhouse-Dantsker, Avia; Nichols, Colin G et al. (2009) Direct regulation of prokaryotic Kir channel by cholesterol. J Biol Chem 284:30727-36
Cheng, Wayland W L; Enkvetchakul, Decha; Nichols, Colin G (2009) KirBac1.1: it's an inward rectifying potassium channel. J Gen Physiol 133:295-305
Enkvetchakul, Decha; Jeliazkova, Iana; Bhattacharyya, Jaya et al. (2007) Control of inward rectifier K channel activity by lipid tethering of cytoplasmic domains. J Gen Physiol 130:329-34