Gating of a G protein-sensitive mammalian Kir3.1 prokaryotic Kir channel chimera in planar lipid bilayers

J Biol Chem. 2010 Dec 17;285(51):39790-800. doi: 10.1074/jbc.M110.151373. Epub 2010 Oct 6.


Kir3 channels control heart rate and neuronal excitability through GTP-binding (G) protein and phosphoinositide signaling pathways. These channels were the first characterized effectors of the βγ subunits of G proteins. Because we currently lack structures of complexes between G proteins and Kir3 channels, their interactions leading to modulation of channel function are not well understood. The recent crystal structure of a chimera between the cytosolic domain of a mammalian Kir3.1 and the transmembrane region of a prokaryotic KirBac1.3 (Kir3.1 chimera) has provided invaluable structural insight. However, it was not known whether this chimera could form functional K(+) channels. Here, we achieved the functional reconstitution of purified Kir3.1 chimera in planar lipid bilayers. The chimera behaved like a bona fide Kir channel displaying an absolute requirement for PIP(2) and Mg(2+)-dependent inward rectification. The channel could also be blocked by external tertiapin Q. The three-dimensional reconstruction of the chimera by single particle electron microscopy revealed a structure consistent with the crystal structure. Channel activity could be stimulated by ethanol and activated G proteins. Remarkably, the presence of both activated Gα and Gβγ subunits was required for gating of the channel. These results confirm the Kir3.1 chimera as a valid structural and functional model of Kir3 channels.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / genetics
  • G Protein-Coupled Inwardly-Rectifying Potassium Channels / chemistry*
  • G Protein-Coupled Inwardly-Rectifying Potassium Channels / genetics
  • HEK293 Cells
  • Humans
  • Ion Channel Gating*
  • Lipid Bilayers / chemistry*
  • Protein Structure, Tertiary
  • Recombinant Fusion Proteins / chemistry*
  • Recombinant Fusion Proteins / genetics
  • Xenopus laevis


  • Bacterial Proteins
  • G Protein-Coupled Inwardly-Rectifying Potassium Channels
  • Lipid Bilayers
  • Recombinant Fusion Proteins