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ATP-dependent substrate transport by the ABC transporter MsbA is proton-coupled.


ABSTRACT: ATP-binding cassette transporters mediate the transbilayer movement of a vast number of substrates in or out of cells in organisms ranging from bacteria to humans. Current alternating access models for ABC exporters including the multidrug and Lipid A transporter MsbA from Escherichia coli suggest a role for nucleotide as the fundamental source of free energy. These models involve cycling between conformations with inward- and outward-facing substrate-binding sites in response to engagement and hydrolysis of ATP at the nucleotide-binding domains. Here we report that MsbA also utilizes another major energy currency in the cell by coupling substrate transport to a transmembrane electrochemical proton gradient. The dependence of ATP-dependent transport on proton coupling, and the stimulation of MsbA-ATPase by the chemical proton gradient highlight the functional integration of both forms of metabolic energy. These findings introduce ion coupling as a new parameter in the mechanism of this homodimeric ABC transporter.

SUBMITTER: Singh H 

PROVIDER: S-EPMC4979069 | biostudies-other | 2016 Aug

REPOSITORIES: biostudies-other

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ATP-dependent substrate transport by the ABC transporter MsbA is proton-coupled.

Singh Himansha H   Velamakanni Saroj S   Deery Michael J MJ   Howard Julie J   Wei Shen L SL   van Veen Hendrik W HW  

Nature communications 20160808


ATP-binding cassette transporters mediate the transbilayer movement of a vast number of substrates in or out of cells in organisms ranging from bacteria to humans. Current alternating access models for ABC exporters including the multidrug and Lipid A transporter MsbA from Escherichia coli suggest a role for nucleotide as the fundamental source of free energy. These models involve cycling between conformations with inward- and outward-facing substrate-binding sites in response to engagement and  ...[more]

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