Structural changes in the cytoplasmic pore of the Kir1.1 channel during pH<sub>i</sub>-gating probed by FRET

<p>Abstract</p> <p>Kir1.1 channels are important in maintaining K<sup>+ </sup>homeostasis in the kidney. Intracellular acidification reversibly closes the Kir1.1 channel and thus decreases K<sup>+ </sup>secretion. In this study, we used Foster resonance ener...

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Bibliographic Details
Main Authors: Shieh Ru-Chi, Lee Jay-Ron
Format: Article
Language:English
Published: BMC 2009-03-01
Series:Journal of Biomedical Science
Online Access:http://www.jbiomedsci.com/content/16/1/29
Description
Summary:<p>Abstract</p> <p>Kir1.1 channels are important in maintaining K<sup>+ </sup>homeostasis in the kidney. Intracellular acidification reversibly closes the Kir1.1 channel and thus decreases K<sup>+ </sup>secretion. In this study, we used Foster resonance energy transfer (FRET) to determine whether the conformation of the cytoplasmic pore changes in response to intracellular pH (pH<sub>i</sub>)-gating in Kir1.1 channels fused with enhanced cyan fluorescent protein (ECFP) and enhanced yellow fluorescent protein (EYFP) (ECFP-Kir1.1-EYFP). Because the fluorescence intensities of ECFP and EYFP were affected at pH<sub>i </sub>< 7.4 where pH<sub>i</sub>-gating occurs in the ECFP-Kir1.1-EYFP construct, we examined the FRET efficiencies of an ECFP-S219R-EYFP mutant, which is completed closed at pH<sub>i </sub>7.4 and open at pH<sub>i </sub>10.0. FRET efficiency was increased from 25% to 40% when the pH<sub>i </sub>was decreased from 10.0 to 7.4. These results suggest that the conformation of the cytoplasmic pore in the Kir1.1 channel changes in response to pH<sub>i </sub>gating such that the N- and C-termini move apart from each other at pH<sub>i </sub>7.4, when the channel is open.</p>
ISSN:1021-7770
1423-0127