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. 1994 May 1;476(3):399–409. doi: 10.1113/jphysiol.1994.sp020141

Mg(2+)-dependent inward rectification of ROMK1 potassium channels expressed in Xenopus oocytes.

C G Nichols 1, K Ho 1, S Hebert 1
PMCID: PMC1160454  PMID: 8057249

Abstract

1. ROMK1 potassium channel currents were examined in Xenopus oocytes by two-microelectrode voltage-clamp and patch-clamp techniques following injection of oocytes with in vitro transcribed ROMK1 cRNA. Macroscopic currents recorded from intact cells rectified inwardly at positive potentials. 2. In inside-out membrane patches rectification is manifested as an apparent reduction of single channel current (at 500 Hz) in the presence of 0.1-10 mM Mg2+, without a decrease in the channel open probability. No inward rectification is observed when membrane patches are isolated into solutions containing potassium as the only internal inorganic cation. 3. Mg2+ block can be described by a simple one-site model for Mg2+ binding with K0 ([Mg2+] causing half-maximal block at 0 mV) of 16.7 mM and delta (the fraction of the membrane field sensed by the blocking Mg2+) of 0.35. 4. The voltage dependence of channel block by cytoplasmic Mg2+ was shifted approximately -50 mV by a reduction in extracellular [K+] from 140 to 0 mM, corresponding to a decrease of K0 to 4.4 mM. 5. At negative membrane potentials, ROMK1 channels exhibit a single subconducting state that is approximately 4/10 of the full conductance. The incidence of subconductance states is not appreciably enhanced in the presence of Mg2+.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Berry R. M., Edmonds D. T. Correlated ion flux through parallel pores: application to channel subconductance states. J Membr Biol. 1993 Apr;133(1):77–84. doi: 10.1007/BF00231879. [DOI] [PubMed] [Google Scholar]
  2. Boulter J., Hollmann M., O'Shea-Greenfield A., Hartley M., Deneris E., Maron C., Heinemann S. Molecular cloning and functional expression of glutamate receptor subunit genes. Science. 1990 Aug 31;249(4972):1033–1037. doi: 10.1126/science.2168579. [DOI] [PubMed] [Google Scholar]
  3. Burnashev N., Schoepfer R., Monyer H., Ruppersberg J. P., Günther W., Seeburg P. H., Sakmann B. Control by asparagine residues of calcium permeability and magnesium blockade in the NMDA receptor. Science. 1992 Sep 4;257(5075):1415–1419. doi: 10.1126/science.1382314. [DOI] [PubMed] [Google Scholar]
  4. Burton F. L., Hutter O. F. Sensitivity to flow of intrinsic gating in inwardly rectifying potassium channel from mammalian skeletal muscle. J Physiol. 1990 May;424:253–261. doi: 10.1113/jphysiol.1990.sp018065. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Ciani S., Ribalet B. Ion permeation and rectification in ATP-sensitive channels from insulin-secreting cells (RINm5F): effects of K+, Na+ and Mg2+. J Membr Biol. 1988 Jul;103(2):171–180. doi: 10.1007/BF01870947. [DOI] [PubMed] [Google Scholar]
  6. Hartmann H. A., Kirsch G. E., Drewe J. A., Taglialatela M., Joho R. H., Brown A. M. Exchange of conduction pathways between two related K+ channels. Science. 1991 Feb 22;251(4996):942–944. doi: 10.1126/science.2000495. [DOI] [PubMed] [Google Scholar]
  7. Heginbotham L., Abramson T., MacKinnon R. A functional connection between the pores of distantly related ion channels as revealed by mutant K+ channels. Science. 1992 Nov 13;258(5085):1152–1155. doi: 10.1126/science.1279807. [DOI] [PubMed] [Google Scholar]
  8. Heginbotham L., MacKinnon R. The aromatic binding site for tetraethylammonium ion on potassium channels. Neuron. 1992 Mar;8(3):483–491. doi: 10.1016/0896-6273(92)90276-j. [DOI] [PubMed] [Google Scholar]
  9. Hille B., Schwarz W. Potassium channels as multi-ion single-file pores. J Gen Physiol. 1978 Oct;72(4):409–442. doi: 10.1085/jgp.72.4.409. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Ho K., Nichols C. G., Lederer W. J., Lytton J., Vassilev P. M., Kanazirska M. V., Hebert S. C. Cloning and expression of an inwardly rectifying ATP-regulated potassium channel. Nature. 1993 Mar 4;362(6415):31–38. doi: 10.1038/362031a0. [DOI] [PubMed] [Google Scholar]
  11. Horie M., Irisawa H., Noma A. Voltage-dependent magnesium block of adenosine-triphosphate-sensitive potassium channel in guinea-pig ventricular cells. J Physiol. 1987 Jun;387:251–272. doi: 10.1113/jphysiol.1987.sp016572. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Kakei M., Noma A., Shibasaki T. Properties of adenosine-triphosphate-regulated potassium channels in guinea-pig ventricular cells. J Physiol. 1985 Jun;363:441–462. doi: 10.1113/jphysiol.1985.sp015721. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Kelly M. E., Dixon S. J., Sims S. M. Inwardly rectifying potassium current in rabbit osteoclasts: a whole-cell and single-channel study. J Membr Biol. 1992 Mar;126(2):171–181. doi: 10.1007/BF00231915. [DOI] [PubMed] [Google Scholar]
  14. Kubo Y., Baldwin T. J., Jan Y. N., Jan L. Y. Primary structure and functional expression of a mouse inward rectifier potassium channel. Nature. 1993 Mar 11;362(6416):127–133. doi: 10.1038/362127a0. [DOI] [PubMed] [Google Scholar]
  15. Kurachi Y. Voltage-dependent activation of the inward-rectifier potassium channel in the ventricular cell membrane of guinea-pig heart. J Physiol. 1985 Sep;366:365–385. doi: 10.1113/jphysiol.1985.sp015803. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. MacKinnon R., Heginbotham L., Abramson T. Mapping the receptor site for charybdotoxin, a pore-blocking potassium channel inhibitor. Neuron. 1990 Dec;5(6):767–771. doi: 10.1016/0896-6273(90)90335-d. [DOI] [PubMed] [Google Scholar]
  17. MacKinnon R., Miller C. Mutant potassium channels with altered binding of charybdotoxin, a pore-blocking peptide inhibitor. Science. 1989 Sep 22;245(4924):1382–1385. doi: 10.1126/science.2476850. [DOI] [PubMed] [Google Scholar]
  18. MacKinnon R., Yellen G. Mutations affecting TEA blockade and ion permeation in voltage-activated K+ channels. Science. 1990 Oct 12;250(4978):276–279. doi: 10.1126/science.2218530. [DOI] [PubMed] [Google Scholar]
  19. Marty A. Blocking of large unitary calcium-dependent potassium currents by internal sodium ions. Pflugers Arch. 1983 Feb;396(2):179–181. doi: 10.1007/BF00615524. [DOI] [PubMed] [Google Scholar]
  20. Matsuda H. Effects of external and internal K+ ions on magnesium block of inwardly rectifying K+ channels in guinea-pig heart cells. J Physiol. 1991 Apr;435:83–99. doi: 10.1113/jphysiol.1991.sp018499. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Matsuda H., Matsuura H., Noma A. Triple-barrel structure of inwardly rectifying K+ channels revealed by Cs+ and Rb+ block in guinea-pig heart cells. J Physiol. 1989 Jun;413:139–157. doi: 10.1113/jphysiol.1989.sp017646. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Matsuda H. Open-state substructure of inwardly rectifying potassium channels revealed by magnesium block in guinea-pig heart cells. J Physiol. 1988 Mar;397:237–258. doi: 10.1113/jphysiol.1988.sp016998. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Matsuda H., Saigusa A., Irisawa H. Ohmic conductance through the inwardly rectifying K channel and blocking by internal Mg2+. Nature. 1987 Jan 8;325(7000):156–159. doi: 10.1038/325156a0. [DOI] [PubMed] [Google Scholar]
  24. Mori H., Masaki H., Yamakura T., Mishina M. Identification by mutagenesis of a Mg(2+)-block site of the NMDA receptor channel. Nature. 1992 Aug 20;358(6388):673–675. doi: 10.1038/358673a0. [DOI] [PubMed] [Google Scholar]
  25. Oliva C., Cohen I. S., Pennefather P. The mechanism of rectification of iK1 in canine Purkinje myocytes. J Gen Physiol. 1990 Aug;96(2):299–318. doi: 10.1085/jgp.96.2.299. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Papazian D. M., Timpe L. C., Jan Y. N., Jan L. Y. Alteration of voltage-dependence of Shaker potassium channel by mutations in the S4 sequence. Nature. 1991 Jan 24;349(6307):305–310. doi: 10.1038/349305a0. [DOI] [PubMed] [Google Scholar]
  27. Sakimura K., Bujo H., Kushiya E., Araki K., Yamazaki M., Yamazaki M., Meguro H., Warashina A., Numa S., Mishina M. Functional expression from cloned cDNAs of glutamate receptor species responsive to kainate and quisqualate. FEBS Lett. 1990 Oct 15;272(1-2):73–80. doi: 10.1016/0014-5793(90)80452-o. [DOI] [PubMed] [Google Scholar]
  28. Takumi T., Ohkubo H., Nakanishi S. Cloning of a membrane protein that induces a slow voltage-gated potassium current. Science. 1988 Nov 18;242(4881):1042–1045. doi: 10.1126/science.3194754. [DOI] [PubMed] [Google Scholar]
  29. Vandenberg C. A. Inward rectification of a potassium channel in cardiac ventricular cells depends on internal magnesium ions. Proc Natl Acad Sci U S A. 1987 Apr;84(8):2560–2564. doi: 10.1073/pnas.84.8.2560. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Wang W. H., Schwab A., Giebisch G. Regulation of small-conductance K+ channel in apical membrane of rat cortical collecting tubule. Am J Physiol. 1990 Sep;259(3 Pt 2):F494–F502. doi: 10.1152/ajprenal.1990.259.3.F494. [DOI] [PubMed] [Google Scholar]
  31. Wang W. H., White S., Geibel J., Giebisch G. A potassium channel in the apical membrane of rabbit thick ascending limb of Henle's loop. Am J Physiol. 1990 Feb;258(2 Pt 2):F244–F253. doi: 10.1152/ajprenal.1990.258.2.F244. [DOI] [PubMed] [Google Scholar]
  32. Wei A., Covarrubias M., Butler A., Baker K., Pak M., Salkoff L. K+ current diversity is produced by an extended gene family conserved in Drosophila and mouse. Science. 1990 May 4;248(4955):599–603. doi: 10.1126/science.2333511. [DOI] [PubMed] [Google Scholar]
  33. Woodhull A. M. Ionic blockage of sodium channels in nerve. J Gen Physiol. 1973 Jun;61(6):687–708. doi: 10.1085/jgp.61.6.687. [DOI] [PMC free article] [PubMed] [Google Scholar]
  34. Yellen G., Jurman M. E., Abramson T., MacKinnon R. Mutations affecting internal TEA blockade identify the probable pore-forming region of a K+ channel. Science. 1991 Feb 22;251(4996):939–942. doi: 10.1126/science.2000494. [DOI] [PubMed] [Google Scholar]
  35. Yellen G. Relief of Na+ block of Ca2+-activated K+ channels by external cations. J Gen Physiol. 1984 Aug;84(2):187–199. doi: 10.1085/jgp.84.2.187. [DOI] [PMC free article] [PubMed] [Google Scholar]

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