title: Symport of proton and sucrose in plasma membrane vesicles isolated from spinach leaves.
abstract: The mechanism of sucrose transport was investigated in plasma membrane (PM) vesicles isolated from spinach (Spinacia oleracea L.) leaves. PM vesicles were isolated by aqueous two-phase partitioning and were equilibrated in pH 7.8 buffer containing K(+). The vesicles rapidly accumulated sucrose in the presence of a transmembrane pH gradient (DeltapH) with external pH set at 5.8. The uptake rate was slow at pH 7.8. The K(+)-selective ionophore, valinomycin, stimulated uptake in the presence of a DeltapH, and the protonophore, carbonyl cyanide m-chlorophenylhydrazone (CCCP), greatly inhibited DeltapH-dependent sucrose uptake. Addition of sucrose to the vesicles resulted in immediate alkalization of the medium. Alkalization was stimulated by valinomycin, was abolished by CCCP, and was sucrose-specific. These results demonstrate the presence of a tightly coupled H(+)/sucrose symporter in PM vesicles isolated from spinach leaves.
authors: Climate Stress Laboratory, Beltsville Agricultural Research Center, U.S. Department of Agriculture, Agricultural Research Service, Beltsville, Maryland 20705.
authors: J H
authors: JH
authors: Slone
authors: T J
authors: TJ
authors: Buckhout
authors: W J
authors: WJ
authors: Vanderwoude