Pore-opening mechanism in trimeric P2X receptor channels.
The opening of ion channels in response to ligand binding, voltage or membrane stretch underlies electrical and chemical signalling throughout biology. Two structural classes of pore-opening mechanisms have been established, including bending of pore-lining helices in the case of tetrameric cation channels, or tilting of such helices in mechanosensitive channels. In this paper, we explore how the structure of the pore changes during opening in P2X receptors by measuring the modification of introduced cysteine residues in transmembrane helices by thiol-reactive reagents, and by engineering metal bridges. Our results are consistent with the X-ray structure of the closed state, and demonstrate that expansion of the gate region in the external pore is accompanied by a significant narrowing of the inner pore, indicating that pore-forming helices straighten on ATP binding to open the channel. This unique pore-opening mechanism has fundamental implications for the role of subunit interfaces in the gating mechanism of P2X receptors and points to a role of the internal pore in ion permeation.
Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA. Mufeng_Li@nih.gov
Mufeng
M
Li
Toshimitsu
T
Kawate
Shai D
SD
Silberberg
Kenton J
KJ
Swartz
D000818:Animals; D004594:Electrophysiology; D057809:HEK293 Cells; D006801:Humans; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D051381:Rats; D058469:Receptors, Purinergic P2X / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D029961:Zebrafish Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
D058469:Receptors, Purinergic P2X; D029961:Zebrafish Proteins