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. 1994 Nov;106(3):991–998. doi: 10.1104/pp.106.3.991

Kinetics Analysis of the Plasma Membrane Sucrose-H+ Symporter from Sugar Beet (Beta vulgaris L.) Leaves.

T J Buckhout 1
PMCID: PMC159623  PMID: 12232379

Abstract

The kinetics behavior of the H+-sucrose (Suc) symporter was investigated in plasma membrane vesicles from sugar beet (Beta vulgaris L.) leaves by analyzing the effect of external and internal pH (pHo and pHi, respectively) on Suc uptake. The apparent Km for Suc uptake increased 18-fold as the pHo increased from 5.5 to 7.5. Over this same pHo range, the apparent Vmax for Suc uptake remained constant. The effects of pHi in the presence or absence of internal Suc were exclusively restricted to changes in Vmax. Thus, proton concentration on the inside of the membrane vesicles ([H+]i) behaved as a noncompetitive inhibitor of Suc uptake. The Km for the proton concentration on the outside of the membrane vesicles was estimated to be pH 6.3, which would indicate that at physiological apoplastic pH Suc transport might be sensitive to changes in pHo. On the other hand, the [H+]i for half-maximal inhibition of Suc uptake was approximately pH 5.4, making regulation of Suc transport through changes in [H+]i unlikely. These results were interpreted in the framework of the kinetics models for co-transport systems developed by D. Sanders, U.-P. Hansen, D. Gradmann, and C. L. Slayman (J Membr Biol [1984] 77: 123-152). Based on their analysis, the behavior of the Suc symporter with respect to the [H+]i is interpreted as an ordered binding mechanism by which the binding of Suc on the apoplastic side of the membrane and its release on the symplastic side precedes that of H+ (i.e. a first-on, first-off model).

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Selected References

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  1. Bradford M. M. A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Anal Biochem. 1976 May 7;72:248–254. doi: 10.1006/abio.1976.9999. [DOI] [PubMed] [Google Scholar]
  2. Bush D. R. Electrogenicity, pH-Dependence, and Stoichiometry of the Proton-Sucrose Symport. Plant Physiol. 1990 Aug;93(4):1590–1596. doi: 10.1104/pp.93.4.1590. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Bush D. R. Proton-Coupled Sucrose Transport in Plasmalemma Vesicles Isolated from Sugar Beet (Beta vulgaris L. cv Great Western) Leaves. Plant Physiol. 1989 Apr;89(4):1318–1323. doi: 10.1104/pp.89.4.1318. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Delrot S., Bonnemain J. L. Involvement of Protons as a Substrate for the Sucrose Carrier during Phloem Loading in Vicia faba Leaves. Plant Physiol. 1981 Mar;67(3):560–564. doi: 10.1104/pp.67.3.560. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Giaquinta R. Phloem Loading of Sucrose: pH Dependence and Selectivity. Plant Physiol. 1977 Apr;59(4):750–755. doi: 10.1104/pp.59.4.750. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Hecht R., Slone J. H., Buckhout T. J., Hitz W. D., Vanderwoude W. J. Substrate Specificity of the H-Sucrose Symporter on the Plasma Membrane of Sugar Beets (Beta vulgaris L.) : Transport of Phenylglucopyranosides. Plant Physiol. 1992 Jun;99(2):439–444. doi: 10.1104/pp.99.2.439. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Komor E., Tanner W. The hexose-proton cotransport system of chlorella. pH-dependent change in Km values and translocation constants of the uptake system. J Gen Physiol. 1974 Nov;64(5):568–581. doi: 10.1085/jgp.64.5.568. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Lemoine R., Gallet O., Gaillard C., Frommer W., Delrot S. Plasma membrane vesicles from source and sink leaves : changes in solute transport and polypeptide composition. Plant Physiol. 1992 Nov;100(3):1150–1156. doi: 10.1104/pp.100.3.1150. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Riesmeier J. W., Hirner B., Frommer W. B. Potato sucrose transporter expression in minor veins indicates a role in phloem loading. Plant Cell. 1993 Nov;5(11):1591–1598. doi: 10.1105/tpc.5.11.1591. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Riesmeier J. W., Willmitzer L., Frommer W. B. Isolation and characterization of a sucrose carrier cDNA from spinach by functional expression in yeast. EMBO J. 1992 Dec;11(13):4705–4713. doi: 10.1002/j.1460-2075.1992.tb05575.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Sanders D. Generalized kinetic analysis of ion-driven cotransport systems: II. Random ligand binding as a simple explanation for non-michaelian kinetics. J Membr Biol. 1986;90(1):67–87. doi: 10.1007/BF01869687. [DOI] [PubMed] [Google Scholar]
  13. Sanders D., Hansen U. P., Gradmann D., Slayman C. L. Generalized kinetic analysis of ion-driven cotransport systems: a unified interpretation of selective ionic effects on Michaelis parameters. J Membr Biol. 1984;77(2):123–152. doi: 10.1007/BF01925862. [DOI] [PubMed] [Google Scholar]
  14. Schwab W. G., Komor E. A possible mechanistic role of the membrane potential in proton-sugar cotransport of Chlorella. FEBS Lett. 1978 Mar 1;87(1):157–160. doi: 10.1016/0014-5793(78)80156-2. [DOI] [PubMed] [Google Scholar]
  15. Tubbe A., Buckhout T. J. In Vitro Analysis of the H-Hexose Symporter on the Plasma Membrane of Sugarbeets (Beta vulgaris L.). Plant Physiol. 1992 Jul;99(3):945–951. doi: 10.1104/pp.99.3.945. [DOI] [PMC free article] [PubMed] [Google Scholar]

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