Maltose/proton co-transport was studied in intact cells and in plasma membrane vesicles of the yeast Saccharomyces cerevisiae. In order to determine uphill transport in vesicles, plasma membranes were fused with proteoliposomes containing cytochrome c oxidase as a proton-motive force-generating system. Maltose accumulation, dependent on the electrical and pH gradients, was observed. The initial uptake velocity and accumulation ratio in vesicles proved to be dependent on the external pH. Moreover, kinetic analysis of maltose transport showed that Vmax. values greatly decreased with increasing pH, whereas the Km remained virtually constant. These observations were in good agreement with results obtained with intact cells, and suggest that proton binding to the carrier proceeds with an apparent pK of 5.7. The observation with intact cells that maltose is co-transported with protons in a one-to-one stoichiometry was ascertained in the vesicle system by measuring the balance between proton-motive force and the chemical maltose gradient. These results show that maltose transport in vesicles prepared by fusion of plasma membranes with cytochrome c oxidase proteoliposomes behaves in a similar way as in intact cells. It is therefore concluded that this vesicle model system offers a wide range of new possibilities for the study of maltose/proton co-transport in more detail.
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June 1992
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Research Article|
June 01 1992
Maltose/proton co-transport in Saccharomyces cerevisiae. Comparative study with cells and plasma membrane vesicles Available to Purchase
C C M Van Leeuwen;
C C M Van Leeuwen
*Department of Medical Biochemistry, Sylvius Laboratory, P.O. Box 9503, 2300 RA Leiden, The Netherlands
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R A Weusthuis;
R A Weusthuis
†Department of Microbiology and Enzymology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands
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E Postma;
E Postma
‡Zaadunie B. V., Westeinde 62, 1600 AA Enkhuizen, The Netherlands
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P J A Van den Broek;
P J A Van den Broek
*Department of Medical Biochemistry, Sylvius Laboratory, P.O. Box 9503, 2300 RA Leiden, The Netherlands
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J P Van Dijken
J P Van Dijken
†Department of Microbiology and Enzymology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands
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Publisher: Portland Press Ltd
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© 1992 The Biochemical Society, London
1992
Biochem J (1992) 284 (2): 441–445.
Citation
C C M Van Leeuwen, R A Weusthuis, E Postma, P J A Van den Broek, J P Van Dijken; Maltose/proton co-transport in Saccharomyces cerevisiae. Comparative study with cells and plasma membrane vesicles. Biochem J 1 June 1992; 284 (2): 441–445. doi: https://doi.org/10.1042/bj2840441
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