Crystal Structure of a Kir3.1-Prokaryotic Kir Channel Chimera
The Kir3.1 K+ channel participates in heart rate control and neuronal excitability through G-protein and lipid signaling pathways. Expression in Escherichia coli has been achieved by replacing three fourths of the transmembrane pore with the pore of a prokaryotic Kir channel, leaving the cytoplasmic pore and membrane interfacial regions of Kir3.1 origin. Two structures were determined at 2.2 Angstroms. The selectivity filter is identical to the Streptomyces lividans K+ channel within error of measurement (r.m.s.d.<0.2 Angstroms), suggesting that K+ selectivity requires extreme conservation of three-dimensional structure. Multiple K+ ions reside within the pore and help to explain voltage-dependent Mg2+ and polyamine blockade and strong rectification. Two constrictions, at the inner helix bundle and at the apex of the cytoplasmic pore, may function as gates: in one structure the apex is open and in the other, it is closed. Gating of the apex is mediated by rigid-body movements of the cytoplasmic pore subunits. Phosphatidylinositol 4, 5-biphosphate-interacting residues suggest a possible mechanism by which the signaling lipid regulates the cytoplasmic pore.
- Research Organization:
- Brookhaven National Laboratory (BNL), Upton, NY (United States). National Synchrotron Light Source (NSLS)
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 959664
- Report Number(s):
- BNL-82650-2009-JA; EMJODG; TRN: US201016%%808
- Journal Information:
- EMBO Journal, Vol. 26; ISSN 0261-4189
- Country of Publication:
- United States
- Language:
- English
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