Conformational changes upon gating of KirBac1.1 into an open-activated state revealed by solid-state NMR and functional assays

Reza Amani, Collin G. Borcik, Nazmul H. Khan, Derek B. Versteeg, Maryam Yekefallah, Hoa Q. Do, Heather R. Coats, Benjamin J. Wylie

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

The conformational changes required for activation and K+ conduction in inward-rectifier K+ (Kir) channels are still debated. These structural changes are brought about by lipid binding. It is unclear how this process relates to fast gating or if the intracellular and extracellular regions of the protein are coupled. Here, we examine the structural details of KirBac1.1 reconstituted into both POPC and an activating lipid mixture of 3:2 POPC:POPG (wt/wt). KirBac1.1 is a prokaryotic Kir channel that shares homology with human Kir channels. We establish that KirBac1.1 is in a constitutively active state in POPC:POPG bilayers through the use of real-time fluorescence quenching assays and Förster resonance energy transfer (FRET) distance measurements. Multidimensional solid-state NMR (SSNMR) spectroscopy experiments reveal two different conformers within the transmembrane regions of the protein in this activating lipid environment, which are distinct from the conformation of the channel in POPC bilayers. The differences between these three distinct channel states highlight conformational changes associated with an open activation gate and suggest a unique allosteric pathway that ties the selectivity filter to the activation gate through interactions between both transmembrane helices, the turret, selectivity filter loop, and the pore helix. We also identify specific residues involved in this conformational exchange that are highly conserved among human Kir channels.

Original languageEnglish
Pages (from-to)2938-2947
Number of pages10
JournalProceedings of the National Academy of Sciences of the United States of America
Volume117
Issue number6
DOIs
StatePublished - Feb 11 2020

Keywords

  • Allostery
  • Lipid activation
  • Membrane protein
  • Potassium channel
  • Solid-state NMR

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