English
 
User Manual Privacy Policy Disclaimer Contact us
  Advanced SearchBrowse

Item

ITEM ACTIONSEXPORT

Released

Journal Article

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

MPS-Authors
/persons/resource/persons137592

Bamberg,  Ernst
Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Max Planck Society;

Locator
There are no locators available
Fulltext (public)
There are no public fulltexts available
Supplementary Material (public)
There is no public supplementary material available
Citation

Derrer, C., Wittek, A., Bamberg, E., Carpaneto, A., Dreyer, I., & Geiger, D. (2013). Conformational Changes Represent the Rate-Limiting Step in the Transport Cycle of Maize SUCROSE TRANSPORTER1. The Plant Cell, 25(8), 3010-3021.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0024-D4B6-7
Abstract
Proton-driven Suc transporters allow phloem cells of higher plants to accumulate Suc to more than 1 M, which is up 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 of the SUT1 protein, alternately exposing the binding pockets to the inward and to the outward face of the membrane.