Click here to close
Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly.
We suggest using a current version of Chrome,
FireFox, or Safari.
Structural determinants of gating in inward-rectifier K+ channels.
Choe H, Palmer LG, Sackin H.
???displayArticle.abstract???
The gating characteristics of two ion channels in the inward-rectifier K+ channel superfamily were compared at the single-channel level. The strong inward rectifier IRK1 (Kir 2.1) opened and closed with kinetics that were slow relative to those of the weakly rectifying ROMK2 (Kir 1.1b). At a membrane potential of -60 mV, both IRK and ROMK had single-exponential open-time distributions, with mean open times of 279 +/- 58 ms (n = 4) for IRK1 and 23 +/- 1 ms (n = 7) for ROMK. At -60 mV (and no EDTA) ROMK2 had two closed times: 1.3 +/- 0.1 and 36 +/- 3 ms (n = 7). Under the same conditions, IRK1 exhibited four discrete closed states with mean closed times of 0.8 +/- 0.1 ms, 14 +/- 0.6 ms, 99 +/- 19 ms, and 2744 +/- 640 ms (n = 4). Both the open and the three shortest closed-time constants of IRK1 decreased monotonically with membrane hyperpolarization. IRK1 open probability (Po) decreased sharply with hyperpolarization due to an increase in the frequency of long closed events that were attributable to divalent-cation blockade. Chelation of divalent cations with EDTA eliminated the slowest closed-time distribution of IRK1 and blunted the hyperpolarization-dependent fall in open probability. In contrast, ROMK2 had shorter open and closed times and only two closed states, and its Po was less affected by hyperpolarization. Chimeric channels were constructed to address the question of which parts of the molecules were responsible for the differences in kinetics. The property of multiple closed states was conferred by the second membrane-spanning domain (M2) of IRK. The long-lived open and closed states, including the higher sensitivity to extracellular divalent cations, correlated with the extracellular loop of IRK, including the "P-region." Channel kinetics were essentially unaffected by the N- and C-termini. The data of the present study are consistent with the idea that the locus of gating is near the outer mouth of the pore.
Aleksandrov,
Inward rectification of the IRK1 K+ channel reconstituted in lipid bilayers.
1996, Pubmed,
Xenbase
Aleksandrov,
Inward rectification of the IRK1 K+ channel reconstituted in lipid bilayers.
1996,
Pubmed
,
Xenbase Chepilko,
Permeation and gating properties of a cloned renal K+ channel.
1995,
Pubmed
,
Xenbase Choe,
Permeation and gating of an inwardly rectifying potassium channel. Evidence for a variable energy well.
1998,
Pubmed
,
Xenbase Diaz,
Interaction of internal Ba2+ with a cloned Ca(2+)-dependent K+ (hslo) channel from smooth muscle.
1996,
Pubmed
,
Xenbase Doi,
Extracellular K+ and intracellular pH allosterically regulate renal Kir1.1 channels.
1996,
Pubmed
,
Xenbase Doyle,
The structure of the potassium channel: molecular basis of K+ conduction and selectivity.
1998,
Pubmed Eisenman,
An introduction to molecular architecture and permeability of ion channels.
1987,
Pubmed Elam,
The role of Mg2+ in the inactivation of inwardly rectifying K+ channels in aortic endothelial cells.
1995,
Pubmed Hagiwara,
Blocking effects of barium and hydrogen ions on the potassium current during anomalous rectification in the starfish egg.
1978,
Pubmed Ho,
Cloning and expression of an inwardly rectifying ATP-regulated potassium channel.
1993,
Pubmed
,
Xenbase Hol,
The role of the alpha-helix dipole in protein function and structure.
1985,
Pubmed Horton,
Engineering hybrid genes without the use of restriction enzymes: gene splicing by overlap extension.
1989,
Pubmed Jan,
Cloned potassium channels from eukaryotes and prokaryotes.
1997,
Pubmed Kubo,
Primary structure and functional expression of a mouse inward rectifier potassium channel.
1993,
Pubmed
,
Xenbase Latorre,
Conduction and selectivity in potassium channels.
1983,
Pubmed Lu,
Electrostatic tuning of Mg2+ affinity in an inward-rectifier K+ channel.
1994,
Pubmed
,
Xenbase Matsuda,
Single inwardly rectifying potassium channels in cultured muscle cells from rat and mouse.
1989,
Pubmed Nichols,
Inward rectifier potassium channels.
1997,
Pubmed Pessia,
Contributions of the C-terminal domain to gating properties of inward rectifier potassium channels.
1995,
Pubmed Robertson,
Inward rectifier K+ currents in smooth muscle cells from rat coronary arteries: block by Mg2+, Ca2+, and Ba2+.
1996,
Pubmed Sakmann,
Voltage-dependent inactivation of inward-rectifying single-channel currents in the guinea-pig heart cell membrane.
1984,
Pubmed Sigworth,
Data transformations for improved display and fitting of single-channel dwell time histograms.
1987,
Pubmed Slesinger,
Identification of structural elements involved in G protein gating of the GIRK1 potassium channel.
1995,
Pubmed
,
Xenbase Taglialatela,
Specification of pore properties by the carboxyl terminus of inwardly rectifying K+ channels.
1994,
Pubmed
,
Xenbase Taglialatela,
C-terminus determinants for Mg2+ and polyamine block of the inward rectifier K+ channel IRK1.
1995,
Pubmed
,
Xenbase Wible,
Gating of inwardly rectifying K+ channels localized to a single negatively charged residue.
1994,
Pubmed
,
Xenbase Yang,
Control of rectification and permeation by residues in two distinct domains in an inward rectifier K+ channel.
1995,
Pubmed
,
Xenbase Zhou,
Primary structure and functional properties of an epithelial K channel.
1994,
Pubmed
,
Xenbase Zhou,
Mutations in the pore region of ROMK enhance Ba2+ block.
1996,
Pubmed
,
Xenbase
