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XB-ART-42639
J Biol Chem 2010 Dec 17;28551:39790-800. doi: 10.1074/jbc.M110.151373.
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Gating of a G protein-sensitive mammalian Kir3.1 prokaryotic Kir channel chimera in planar lipid bilayers.

Leal-Pinto E , Gómez-Llorente Y , Sundaram S , Tang QY , Ivanova-Nikolova T , Mahajan R , Baki L , Zhang Z , Chavez J , Ubarretxena-Belandia I , Logothetis DE .


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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.

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Species referenced: Xenopus laevis
Genes referenced: kcnj3

References [+] :
Aleksandrov, Inward rectification of the IRK1 K+ channel reconstituted in lipid bilayers. 1996, Pubmed, Xenbase