title: Sucrose-dependent H(+) transport in plasma-membrane vesicles isolated from sugarbeet leaves (Beta vulgaris L.) : Evidence in support of the H(+)-symport model for sucrose transport.
abstract: The mechanism of sucrose transport across the plasma membrane (PM) was investigated in membrane vesicles isolated from sugarbeet (Beta vulgaris L.) leaves. In the presence of a membrane potential (Δψ) generated as a K(+)-diffusion potential, negative inside, sucrose induced a rapid and transient alkalization of the medium. Alkalization was inhibited by carbonyl cyanide m-chlorophenylhydrazone, was specific for the sucrose sugar and was dependent on the sucrose concentration with a Km of approx. 1 mM. Sucrose-induced alkalization and sucrose transport were inhibited by the sulfhydryl-reactive reagent, p-chloromercuribenzene sulfonic acid, and by the histidine-reactive reagent, diethyl pyrocarbonate. Parallel analysis of sucrose uptake and alkalization indicated that the stoichiometry of sucrose uptake to proton consumed was 1∶1. These results provide clear evidence that the saturable mechanism of sucrose transport across the PM in plants is a coupled H(+)-sucrose symport.
authors.affiliation: Plant Photobiology Laboratory, Beltsville Agricultural Research Center, USDA-Agricultural Research Service, 20705, Beltsville, MD, USA.
authors.forename: J H
authors.initials: JH
authors.lastname: Slone
authors.forename: T J
authors.initials: TJ
authors.lastname: Buckhout