Sucrose protectable inhibition of the sucrose transporter by N-ethylmaleimide

To understand contradictory data published in the literature, the sensitivity of sucrose and of valine uptake to N-ethylmaleimide (NEM) was reinvestigated in detail with plasma membrane vesicles purified by phase partitioning from mature sugar beet (Beta vulgaris) leaves. Uptake in the vesicles was...

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Bibliographic Details
Published in:Journal of experimental botany 1994-08, Vol.45 (8), p.1091-1096
Main Authors: Sakr, Soulaimane, Gaillard, Cecile, Roblin, Gabriel, Delrot, Serge
Format: Article
Language:English
Subjects:
Absorption. Translocation of ions and substances. Permeability
Agronomy. Soil science and plant productions
Biological and medical sciences
Cell membranes
Cell physiology
differential labelling
Economic plant physiology
Fundamental and applied biological sciences. Psychology
Leaves
Nutrition. Photosynthesis. Respiration. Metabolism
Plant physiology
Plant physiology and development
Plants
plasma membrane
Plasma membrane and permeation
Pretreatment
Protons
Reagents
Sugar beets
Sugar transport
Temperature control
thiol reagents
Thiols
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Summary:To understand contradictory data published in the literature, the sensitivity of sucrose and of valine uptake to N-ethylmaleimide (NEM) was reinvestigated in detail with plasma membrane vesicles purified by phase partitioning from mature sugar beet (Beta vulgaris) leaves. Uptake in the vesicles was energized by an artificial proton-motive force combining a pH gradient and an electrical gradient. Three main parameters were varied in the experiments: the presence of a reducing agent, dlthiothreitol (DTT) In the medium used to store the vesicles, the temperature of pretreatment with NEM (12 or 23°C) and the temperature of incubation with the labelled substrate (12 or 23°C). Sensitivity of sucrose uptake to NEM only appeared with vesicles that had been stored in the presence of DTT, and if the pretreatment was run at 23°C. The temperature of incubation with labelled sucrose did not affect NEM sensitivity. The NEM sensitivity of valine uptake was not affected in the same way as sucrose uptake by the temperature of preincubation, showing that the effects observed were specific for a given transporter. Under conditions which normally inhibit sucrose uptake, addition of sucrose during NEM pretreatment protected the sucrose transporter against NEM inhibition.
ISSN:0022-0957
1460-2431
DOI:10.1093/jxb/45.8.1091