Remodelling of the SUR-Kir6.2 interface of the KATP channel upon ATP binding revealed by the conformational blocker rhodamine 123.
The Journal of Physiology. 2007-06-25; 582(1): 27-39
DOI: 10.1113/jphysiol.2007.134288
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1. J Physiol. 2007 Jul 1;582(Pt 1):27-39. Epub 2007 May 17.
Remodelling of the SUR-Kir6.2 interface of the KATP channel upon ATP binding
revealed by the conformational blocker rhodamine 123.
Hosy E(1), Dérand R, Revilloud J, Vivaudou M.
Author information:
(1)Institute of Structural Biology, UMR5075 CEA-CNRS-University J. Fourier, 41,
rue Jules Horowitz, 38027 Grenoble, France.
ATP-sensitive K+ channels (K(ATP) channels) are metabolic sensors formed by
association of a K+ channel, Kir6, and an ATP-binding cassette (ABC) protein,
SUR, which allosterically regulates channel gating in response to nucleotides and
pharmaceutical openers and blockers. How nucleotide binding to SUR translates
into modulation of Kir6 gating remains largely unknown. To address this issue, we
have used a novel conformational KATP channel inhibitor, rhodamine 123 (Rho123)
which targets the Kir6 subunit in a SUR-dependent manner. Rho123 blocked SUR-less
Kir6.2 channels with an affinity of approximately 1 microM, regardless of the
presence of nucleotides, but it had no effect on channels formed by the
association of Kir6.2 and the N-terminal transmembrane domain TMD0 of SUR. Rho123
blocked SUR + Kir6.2 channels with the same affinity as Kir6.2 but this effect
was antagonized by ATP. Protection from Rho123 block by ATP was due to direct
binding of ATP to SUR and did not entail hydrolysis because it was not mimicked
by AMP, did not require Mg2+ and was reduced by mutations in the
nucleotide-binding domains of SUR. These results suggest that Rho123 binds at the
TMD0-Kir6.2 interface and that binding of ATP to SUR triggers a change in the
structure of the contact zone between Kir6.2 and domain TMD0 of SUR that causes
masking of the Rho123 site on Kir6.2.
DOI: 10.1113/jphysiol.2007.134288
PMCID: PMC2075286
PMID: 17510180 [Indexed for MEDLINE]