Abstract
1. Various ways of computing the proton stoichiometry of glycine absorption were examined in relation to the problem of distinguishing the proton flow (i) through the symport from the basal proton flow (ii) outside it. By depolarizing the plasma membrane, i will tend to inhibit ii. 2. A series of 23 yeast (Saccharomyces carlsbergensis) preparations grown with proline or glutamate were used, some of which were starved in the presence of glucose. Consequently, after ATP depletion, the rate of glycine uptake from a 0.2 mM solution varied through the series from 3 to 14 nmol.min-1.mg-1. Basal proton uptake in the absence of glycine was fairly constant at 3-4 nmol.min-1.mg-1. 3. After addition of glycine, the number of extra equivalents of protons entering the yeast with each amino acid equivalent in 30 s was 0.5 at the lowest rate of glycine absorption and 1.8 equivalents at the fastest rate. However, total proton absorption in 30 s increased in direct proportion to the amount of glycine absorbed. The proportionality factor, indicative of the carrier stoichiometry, was 2.25 +/- 0.13 (23) S.E.M. The effective basal proton uptake was negligibly small. 4. Progress of proton and glycine absorption by each yeast preparation in the period up to 180 s fitted the mathematical model described in the preceding paper by Eddy, Hopkins & Johnson [(1988) Biochem. J. 251, 111-114]. The analysis led to two estimates of the constant ratio of the inflow of protons to the inflow of glycine that would apply when the basal proton flow vanished. These further estimates of the carrier stoichiometry were also near 2, being 2.07 +/- 0.24 (6) and 2.22 +/- 0.07 (17).
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Selected References
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- Ballarin-Denti A., Den Hollander J. A., Sanders D., Slayman C. W., Slayman C. L. Kinetics and pH-dependence of glycine-proton symport in Saccharomyces cerevisiae. Biochim Biophys Acta. 1984 Nov 21;778(1):1–16. doi: 10.1016/0005-2736(84)90442-5. [DOI] [PubMed] [Google Scholar]
- Cockburn M., Earnshaw P., Eddy A. A. The stoicheiometry of the absorption of protons with phosphate and L-glutamate by yeasts of the genus Saccharomyces. Biochem J. 1975 Mar;146(3):705–712. doi: 10.1042/bj1460705. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Eddy A. A., Hopkins P. G. The putative electrogenic nitrate-proton symport of the yeast Candida utilis. Comparison with the systems absorbing glucose or lactate. Biochem J. 1985 Oct 15;231(2):291–297. doi: 10.1042/bj2310291. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Eddy A. A., Hopkins P., Johnson E. R. Use of progress curves to estimate the co-substrate-to-substrate flow ratio of a symport mechanism. Application to the isoleucine-Na+ symport of mouse ascites-tumour cells and to the lactose-proton symport. Biochem J. 1988 Apr 1;251(1):111–114. doi: 10.1042/bj2510111. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Eddy A. A., Nowacki J. A. Stoicheiometrical proton and potassium ion movements accompanying the absorption of amino acids by the yeast Saccharomyces carlsbergensis. Biochem J. 1971 May;122(5):701–711. doi: 10.1042/bj1220701. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Grenson M., Hou C., Crabeel M. Multiplicity of the amino acid permeases in Saccharomyces cerevisiae. IV. Evidence for a general amino acid permease. J Bacteriol. 1970 Sep;103(3):770–777. doi: 10.1128/jb.103.3.770-777.1970. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kimmich G. A., Randles J. Sodium-sugar coupling stoichiometry in chick intestinal cells. Am J Physiol. 1984 Jul;247(1 Pt 1):C74–C82. doi: 10.1152/ajpcell.1984.247.1.C74. [DOI] [PubMed] [Google Scholar]
- Philo R. D., Eddy A. A. Equilibrium and steady-state models of the coupling between the amino acid gradient and the sodium electrochemical gradient in mouse ascites- tumour cells. Biochem J. 1978 Sep 15;174(3):811–817. doi: 10.1042/bj1740811. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Sanders D., Slayman C. L., Pall M. L. Stoichiometry of H+/amino acid cotransport in Neurospora crassa revealed by current-voltage analysis. Biochim Biophys Acta. 1983 Oct 26;735(1):67–76. doi: 10.1016/0005-2736(83)90261-4. [DOI] [PubMed] [Google Scholar]
- Seaston A., Carr G., Eddy A. A. The concentration of glycine by preparations of the yeast Saccharomyces Carlsbergensis depleted of adenosine triphosphate: Effects of proton gradients and uncoupling agents. Biochem J. 1976 Mar 15;154(3):669–676. doi: 10.1042/bj1540669. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Seaston A., Inkson C., Eddy A. A. The absorption of protons with specific amino acids and carbohydrates by yeast. Biochem J. 1973 Aug;134(4):1031–1043. doi: 10.1042/bj1341031. [DOI] [PMC free article] [PubMed] [Google Scholar]