Implications for cytoplasmic pH, protonmotice force, and amino-acid transport across the plasmalemma of Riccia fluitans Article Received: 08 January 1987 Accepted: 14 April 1987 DOI:
10.1007/BF00403028 Cite this article as: Johannes, E. & Felle, H. Planta (1987) 172: 53. doi:10.1007/BF00403028 Abstract
By means of pH-sensitive microelectrodes, cytoplasmic pH has been monitored continuously during amino-acid transport across the plasmalemma of
Riccia fluitans rhizoid cells under various experimental conditions. (i) Contrary to the general assumption that import of amino acids (or hexoses) together with protons should lead to cytoplasmic acidification, an alkalinization of 0.1–0.3 pH c units was found for all amino acids tested. Similar alkalinizations were recorded in the presence of hexoses and methylamine. No alkalinization occurred when the substrates were added in the depolarized state or in the presence of cyanide, where the electrogenic H +-pump is inhibited. (ii) After acidification of the cytoplasm by means of various concentrations of acetic acid, amino-acid transport is massively altered, although the protonmotive force remained essentially constant. It is suggested that H +-cotransport is energetically interconnected with the proton-export pump which is stimulated by the amino-acid-induced depolarization, thus causing proton depletion of the cytoplasm. It is concluded that, in order to investigate H +-dependent cotransport processes, the cytoplasmic pH must be measured and be under continuous experimental control; secondly, neither ΔpH nor the protonmotive force across a membrane are reliable quantities for analysing a proton-dependent process. Key words Amino acid transport Cytoplasmic pH Protonmotive force Riccia Abbreviations 3-OMG
electrical potential difference across the respective membrane, i.e. membrane potential
Δμ H+/F (=pmf)
electrochemical proton gradient
Ballarin-Denti, A., Den Hollander, J.A., Sanders, D., Slayman, C.W., Slayman, C.L. (1984) Kinetics and pH-dependence of glycine-proton symport in
. Biochim. Biophys. Acta
Bates, G.W., Goldsmith, M.H.M. (1983) Rapid response of the plasma-membrane potential in oat coleoptiles to auxin and other weak acids. Planta
Bertl, A., Felle, H. (1985) Cytoplasmic pH of root hair cells of
recorded by a pH-sensitive microelectrode. Does fusicoccin stimulate the proton pump by cytoplasmic acidification? J. Exp. Bot.
Cho, B.-H., Komor, E. (1984) Mechanism of arginine transport in
Etherton, B., Rubinstein, B. (1978) Evidence for amino acid-H
cotransport in oat coleoptiles. Plant Physiol.
Felle, H. (1980) Amine transport at the plasmalemma of
. Biochim. Biophys. Acta
Felle, H. (1981) Stereospecificity and electrogenicity of amino acid transport in
Felle, H. (1983) Driving forces and current-voltage characteristics of amino acid transport in
. Biochim. Biophys. Acta
Felle, H. (1984) Steady-state current-voltage characteristics of amino acid transport in rhizoid cells of
. Is the carrier negatively charged? Biochim. Biophys. Acta
Felle, H. (1987) Proton transport and pH control in
root hairs: A study carried out with double-barrelled pH-microelectrodes. J. Exp. Bot.
Felle, H., Bentrup, F.W. (1980) Hexose transport and membrane depolarization in
Felle, H., Bertl, A. (1986) The fabrication of H
-selective liquid-membrane microelectrodes for use in plant cells. J. Exp. Bot.
Fischer, E., Lüttge, U. (1980) Membrane potential changes related to active transport of glycine in
GL. Plant Physiol.
Hauer, R., Höfer, M. (1982) Variable H
/substrate stoichiometries in
are caused by a pH-dependent protonation of the carrier (s). Biochem. J.
Johannes, E., Felle, H. (1985) Transport of basic amino acids in
: Evidence for a second binding site. Planta
Jung, K.D., Lüttge, U. (1980) Amino acid uptake by
by a mechanism with affinity to neutral
-amino acids. Planta
Komor, E., Tanner, W. (1974) The hexose-proton cotransport system of
: pH-dependent change in K
values and translocation constants of the uptake system. J. Gen. Physiol.
Komor, E., Tanner, W. (1976) The determination of the membrane potential of
. Evidence for electrogenic sugar transport. Eur. J. Biochem.
Sanders, D., Hansen, U.-P., Gradmann, D., Slayman, C.L. (1984) Generalized kinetic analysis of ion-driven cotransport systems: A unified interpretation of selective ionic effects on Michaelis parameters. J. Membr. Biol.
Sanders, D., Hansen, U.-P., Gradmann, D., Slayman, C.L. (1981) Role of the plasma membrane proton pump in pH regulation in nonanimal cells. Proc. Natl. Acad. Sci. USA
Sanders, D., Slayman, C.L. (1982) Predominant role of oxidative metabolism, not proton transport, in the cucaryotic microorganism
. J. Gen. Physiol.
Seaston, A., Inkson, C., Eddy, A.A. (1973) The absorption of protons with specific amino acids and carbohydrates by yeast. Biochem. J.
Slayman, G.L., Slayman, C.W. (1974) Depolarization of the plasmalemma of
during active transport of glucose: Evidence for a proton-dependent cotransport system. Proc. Natl. Acad. Sci. USA
Smith, F.A., Raven, J.A. (1979) Intracellular pH and its regulation. Annu. Rev. Plant Physiol.