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Nucleotide inhibition of the pancreatic ATP-sensitive K+ channel explored with patch-clamp fluorometry

Authors :
Samuel G Usher
Frances M Ashcroft
Michael C Puljung
Source :
eLife, Vol 9 (2020)
Publication Year :
2020
Publisher :
eLife Sciences Publications Ltd, 2020.

Abstract

Pancreatic ATP-sensitive K+ channels (KATP) comprise four inward rectifier subunits (Kir6.2), each associated with a sulphonylurea receptor (SUR1). ATP/ADP binding to Kir6.2 shuts KATP. Mg-nucleotide binding to SUR1 stimulates KATP. In the absence of Mg2+, SUR1 increases the apparent affinity for nucleotide inhibition at Kir6.2 by an unknown mechanism. We simultaneously measured channel currents and nucleotide binding to Kir6.2. Fits to combined data sets suggest that KATP closes with only one nucleotide molecule bound. A Kir6.2 mutation (C166S) that increases channel activity did not affect nucleotide binding, but greatly perturbed the ability of bound nucleotide to inhibit KATP. Mutations at position K205 in SUR1 affected both nucleotide affinity and the ability of bound nucleotide to inhibit KATP. This suggests a dual role for SUR1 in KATP inhibition, both in directly contributing to nucleotide binding and in stabilising the nucleotide-bound closed state.

Details

Language :
English
ISSN :
2050084X
Volume :
9
Database :
Directory of Open Access Journals
Journal :
eLife
Publication Type :
Academic Journal
Accession number :
edsdoj.03955459d3cc4cbbaa1a59ccc81000a1
Document Type :
article
Full Text :
https://doi.org/10.7554/eLife.52775