Skip to main content
PMC home page
The Journal of General Physiology logoLink to The Journal of General Physiology
. 1994 May 1;103(5):807–831. doi: 10.1085/jgp.103.5.807

External pH effects on the depolarization-activated K channels in guard cell protoplasts of Vicia faba

PMCID: PMC2219221  PMID: 8035163

Abstract

Previous studies reveal that the pH of the apoplastic solution in the guard cell walls may vary between 7.2 and 5.1 in closed and open stomata, respectively. During these aperture and pH changes, massive K+ fluxes cross the cellular plasma membrane driving the osmotic turgor and volume changes of guard cells. Therefore, we examined the effect of extracellular pH on the depolarization-activated K channels (KD channels), which constitute the K+ efflux pathway, in the plasma membrane of Vicia faba guard cell protoplasts. We used patch clamp, both in whole cells as well as in excised outside-out membrane patches. Approximately 500 KD channels, at least, could be activated by depolarization in one protoplast (density: approximately 0.6 micron-2). Acidification from ph 8.1 to 4.4 decreased markedly the whole-cell conductance, GK, of the KD channels, shifted its voltage dependence, GK- EM, to the right on the voltage axis, slowed the rate of activation and increased the rate of deactivation, whereas the single channel conductance was not affected significantly. Based on the GK-EM shifts, the estimated average negative surface charge spacing near the KD channel is 39 A. To quantify the effects of protons on the rates of transitions between the hypothesized conformational states of the channels, we fitted the experimental macroscopic steady state conductance-voltage relationship and the voltage dependence of time constants of activation and deactivation, simultaneously, with a sequential three-state model CCO. In terms of this model, protonation affects the voltage-dependent properties via a decrease in localized, rather than homogeneous, surface charge sensed by the gating moieties. In terms of either the CO or CCO model, the protonation of a site with a pKa of 4.8 decreases the voltage-independent number of channels, N, that are available for activation by depolarization.

Full Text

The Full Text of this article is available as a PDF (1.5 MB).

Selected References

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

  1. Anderson J. A., Huprikar S. S., Kochian L. V., Lucas W. J., Gaber R. F. Functional expression of a probable Arabidopsis thaliana potassium channel in Saccharomyces cerevisiae. Proc Natl Acad Sci U S A. 1992 May 1;89(9):3736–3740. doi: 10.1073/pnas.89.9.3736. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Armstrong C. M. Inactivation of the potassium conductance and related phenomena caused by quaternary ammonium ion injection in squid axons. J Gen Physiol. 1969 Nov;54(5):553–575. doi: 10.1085/jgp.54.5.553. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Balser J. R., Roden D. M., Bennett P. B. Global parameter optimization for cardiac potassium channel gating models. Biophys J. 1990 Mar;57(3):433–444. doi: 10.1016/S0006-3495(90)82560-1. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Becchetti A., Arcangeli A., Del Bene M. R., Olivotto M., Wanke E. Intra and extracellular surface charges near Ca2+ channels in neurons and neuroblastoma cells. Biophys J. 1992 Oct;63(4):954–965. doi: 10.1016/S0006-3495(92)81665-X. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Begenisich T., Danko M. Hydrogen ion block of the sodium pore in squid giant axons. J Gen Physiol. 1983 Nov;82(5):599–618. doi: 10.1085/jgp.82.5.599. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Begenisich T. Magnitude and location of surface charges on Myxicola giant axons. J Gen Physiol. 1975 Jul;66(1):47–65. doi: 10.1085/jgp.66.1.47. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Behrens M. I., Oberhauser A., Bezanilla F., Latorre R. Batrachotoxin-modified sodium channels from squid optic nerve in planar bilayers. Ion conduction and gating properties. J Gen Physiol. 1989 Jan;93(1):23–41. doi: 10.1085/jgp.93.1.23. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Blatt M. R. Ion channel gating in plants: physiological implications and integration for stomatal function. J Membr Biol. 1991 Nov;124(2):95–112. doi: 10.1007/BF01870455. [DOI] [PubMed] [Google Scholar]
  9. Blatt M. R. K+ channels of stomatal guard cells. Characteristics of the inward rectifier and its control by pH. J Gen Physiol. 1992 Apr;99(4):615–644. doi: 10.1085/jgp.99.4.615. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Cao Y., Anderova M., Crawford N. M., Schroeder J. I. Expression of an outward-rectifying potassium channel from maize mRNA and complementary RNA in Xenopus oocytes. Plant Cell. 1992 Aug;4(8):961–969. doi: 10.1105/tpc.4.8.961. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Carbone E., Fioravanti R., Prestipino G., Wanke E. Action of extracellular pH on Na+ and K+ membrane currents in the giant axon of Loligo vulgaris. J Membr Biol. 1978 Nov 8;43(4):295–315. doi: 10.1007/BF01871693. [DOI] [PubMed] [Google Scholar]
  12. Chung S. K., Reinhart P. H., Martin B. L., Brautigan D., Levitan I. B. Protein kinase activity closely associated with a reconstituted calcium-activated potassium channel. Science. 1991 Aug 2;253(5019):560–562. doi: 10.1126/science.1857986. [DOI] [PubMed] [Google Scholar]
  13. Draber S., Schultze R., Hansen U. P. Cooperative behavior of K+ channels in the tonoplast of Chara corallina. Biophys J. 1993 Oct;65(4):1553–1559. doi: 10.1016/S0006-3495(93)81194-9. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Ehrenstein G., Blumenthal R., Latorre R., Lecar H. Kinetics of the opening and closing of individual excitability-inducing material channels in a lipid bilayer. J Gen Physiol. 1974 Jun;63(6):707–721. doi: 10.1085/jgp.63.6.707. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Gilbert D. L., Ehrenstein G. Effect of divalent cations on potassium conductance of squid axons: determination of surface charge. Biophys J. 1969 Mar;9(3):447–463. doi: 10.1016/S0006-3495(69)86396-4. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Gilbert D. L., Ehrenstein G. Use of a fixed charge model to determine the pK of the negative sites on the external membrane surface. J Gen Physiol. 1970 Jun;55(6):822–825. [PMC free article] [PubMed] [Google Scholar]
  17. HODGKIN A. L., HUXLEY A. F. A quantitative description of membrane current and its application to conduction and excitation in nerve. J Physiol. 1952 Aug;117(4):500–544. doi: 10.1113/jphysiol.1952.sp004764. [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Hagiwara S., Miyazaki S., Moody W., Patlak J. Blocking effects of barium and hydrogen ions on the potassium current during anomalous rectification in the starfish egg. J Physiol. 1978 Jun;279:167–185. doi: 10.1113/jphysiol.1978.sp012338. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Hamill O. P., Marty A., Neher E., Sakmann B., Sigworth F. J. Improved patch-clamp techniques for high-resolution current recording from cells and cell-free membrane patches. Pflugers Arch. 1981 Aug;391(2):85–100. doi: 10.1007/BF00656997. [DOI] [PubMed] [Google Scholar]
  20. Hanke W., Miller C. Single chloride channels from Torpedo electroplax. Activation by protons. J Gen Physiol. 1983 Jul;82(1):25–45. doi: 10.1085/jgp.82.1.25. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Hartung W., Radin J. W., Hendrix D. L. Abscisic Acid Movement into the Apoplastic solution of Water-Stressed Cotton Leaves: Role of Apoplastic pH. Plant Physiol. 1988 Mar;86(3):908–913. doi: 10.1104/pp.86.3.908. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Huang L. Y., Catterall W. A., Ehrenstein G. Selectivity of cations and nonelectrolytes for acetylcholine-activated channels in cultured muscle cells. J Gen Physiol. 1978 Apr;71(4):397–410. doi: 10.1085/jgp.71.4.397. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Huang L. Y., Moran N., Ehrenstein G. Gating kinetics of batrachotoxin-modified sodium channels in neuroblastoma cells determined from single-channel measurements. Biophys J. 1984 Jan;45(1):313–322. doi: 10.1016/S0006-3495(84)84157-0. [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. Iwasa K., Ehrenstein G., Moran N., Jia M. Evidence for interactions between batrachotoxin-modified channels in hybrid neuroblastoma cells. Biophys J. 1986 Sep;50(3):531–537. doi: 10.1016/S0006-3495(86)83491-9. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Ketchum K. A., Shrier A., Poole R. J. Characterization of potassium-dependent currents in protoplasts of corn suspension cells. Plant Physiol. 1989 Apr;89(4):1184–1192. doi: 10.1104/pp.89.4.1184. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Kruse T., Tallman G., Zeiger E. Isolation of Guard Cell Protoplasts from Mechanically Prepared Epidermis of Vicia faba Leaves. Plant Physiol. 1989 Aug;90(4):1382–1386. doi: 10.1104/pp.90.4.1382. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Moran N., Ehrenstein G., Iwasa K., Mischke C., Bare C., Satter R. L. Potassium Channels in Motor Cells of Samanea saman: A Patch-Clamp Study. Plant Physiol. 1988 Nov;88(3):643–648. doi: 10.1104/pp.88.3.643. [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Moran N., Fox D., Satter R. L. Interaction of the Depolarization-Activated K Channel of Samanea saman with Inorganic Ions: A Patch-Clamp Study. Plant Physiol. 1990 Oct;94(2):424–431. doi: 10.1104/pp.94.2.424. [DOI] [PMC free article] [PubMed] [Google Scholar]
  29. Mozhayeva G. N., Naumov A. P. Effect of surface charge on the steady-state potassium conductance of nodal membrane. Nature. 1970 Oct 10;228(5267):164–165. doi: 10.1038/228164a0. [DOI] [PubMed] [Google Scholar]
  30. Schachtman D. P., Schroeder J. I., Lucas W. J., Anderson J. A., Gaber R. F. Expression of an inward-rectifying potassium channel by the Arabidopsis KAT1 cDNA. Science. 1992 Dec 4;258(5088):1654–1658. doi: 10.1126/science.8966547. [DOI] [PubMed] [Google Scholar]
  31. Schauf C. L., Davis F. A. Sensitivity of the sodium and potassium channels of Myxicola giant axons to changes in external pH. J Gen Physiol. 1976 Feb;67(2):185–195. doi: 10.1085/jgp.67.2.185. [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. Schauf C. L. The interactions of calcium with mpyxicola giant axons and a description in terms of a simple surface charge model. J Physiol. 1975 Jul;248(3):613–624. doi: 10.1113/jphysiol.1975.sp010991. [DOI] [PMC free article] [PubMed] [Google Scholar]
  33. Schauf C. L., Wilson K. J. Effects of abscisic acid on K+ channels in Vicia faba guard cell protoplasts. Biochem Biophys Res Commun. 1987 May 29;145(1):284–290. doi: 10.1016/0006-291x(87)91318-0. [DOI] [PubMed] [Google Scholar]
  34. Schroeder J. I. K+ transport properties of K+ channels in the plasma membrane of Vicia faba guard cells. J Gen Physiol. 1988 Nov;92(5):667–683. doi: 10.1085/jgp.92.5.667. [DOI] [PMC free article] [PubMed] [Google Scholar]
  35. Schroeder J. I. Quantitative analysis of outward rectifying K+ channel currents in guard cell protoplasts from Vicia faba. J Membr Biol. 1989 Mar;107(3):229–235. doi: 10.1007/BF01871938. [DOI] [PubMed] [Google Scholar]
  36. Schroeder J. I., Raschke K., Neher E. Voltage dependence of K channels in guard-cell protoplasts. Proc Natl Acad Sci U S A. 1987 Jun;84(12):4108–4112. doi: 10.1073/pnas.84.12.4108. [DOI] [PMC free article] [PubMed] [Google Scholar]
  37. Sentenac H., Bonneaud N., Minet M., Lacroute F., Salmon J. M., Gaymard F., Grignon C. Cloning and expression in yeast of a plant potassium ion transport system. Science. 1992 May 1;256(5057):663–665. doi: 10.1126/science.1585180. [DOI] [PubMed] [Google Scholar]
  38. Shrager P. Ionic conductance changes in voltage clamped crayfish axons at low pH. J Gen Physiol. 1974 Dec;64(6):666–690. doi: 10.1085/jgp.64.6.666. [DOI] [PMC free article] [PubMed] [Google Scholar]
  39. Spires S., Begenisich T. Modification of potassium channel kinetics by amino group reagents. J Gen Physiol. 1992 Jan;99(1):109–129. doi: 10.1085/jgp.99.1.109. [DOI] [PMC free article] [PubMed] [Google Scholar]
  40. Ueno S., Nakaye T., Akaike N. Proton-induced sodium current in freshly dissociated hypothalamic neurones of the rat. J Physiol. 1992 Feb;447:309–327. doi: 10.1113/jphysiol.1992.sp019004. [DOI] [PMC free article] [PubMed] [Google Scholar]
  41. Van Duijn B. Hodgkin-Huxley analysis of whole-cell outward rectifying K(+)-currents in protoplasts from tobacco cell suspension cultures. J Membr Biol. 1993 Feb;132(1):77–85. doi: 10.1007/BF00233053. [DOI] [PubMed] [Google Scholar]
  42. 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]
  43. Zhang J. F., Siegelbaum S. A. Effects of external protons on single cardiac sodium channels from guinea pig ventricular myocytes. J Gen Physiol. 1991 Dec;98(6):1065–1083. doi: 10.1085/jgp.98.6.1065. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from The Journal of General Physiology are provided here courtesy of The Rockefeller University Press

RESOURCES