Conformational Changes Represent the Rate-Limiting Step in the Transport Cycle of Maize SUCROSE TRANSPORTER1

Derrer, Carmen; Wittek, Anke; Bamberg, Ernst; Carpaneto, Armando; Dreyer, Ingo; Geiger, Dietmar


Proton-driven Suc transporters allow phloem cells of higher plants to accumulate Suc to more than 1 M, which is up to; similar to 1000-fold higher than in the surrounding extracellular space. The carrier protein can accomplish this task only because proton and Suc transport are tightly coupled. This study provides insights into this coupling by resolving the first step in the transport cycle of the Suc transporter SUT1 from maize (Zea mays). Voltage clamp fluorometry measurements combining electrophysiological techniques with fluorescence-based methods enable the visualization of conformational changes of SUT1 expressed in Xenopus laevis oocytes. Using the Suc derivate sucralose, binding of which hinders conformational changes of SUT1, the association of protons to the carrier could be dissected from transport-associated movements of the protein. These combined approaches enabled us to resolve the binding of protons to the carrier and its interrelationship with the alternating movement of the protein. The data indicate that the rate-limiting step of the reaction cycle is determined by the accessibility of the proton binding site. This, in turn, is determined by the conformational change

Más información

Título según WOS: ID WOS:000324920500022 Not found in local WOS DB
Título de la Revista: PLANT CELL
Volumen: 25
Número: 8
Fecha de publicación: 2013
Página de inicio: 3010
Página final: 3021


Notas: ISI