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

Himansha Singh, Saroj Velamakanni, Michael J. Deery, Julie Howard, Shen L. Wei and Hendrik W. van Veen ()
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Himansha Singh: University of Cambridge
Saroj Velamakanni: University of Cambridge
Michael J. Deery: Cambridge Centre for Proteomics, University of Cambridge
Julie Howard: Cambridge Centre for Proteomics, University of Cambridge
Shen L. Wei: University of Cambridge
Hendrik W. van Veen: University of Cambridge

Nature Communications, 2016, vol. 7, issue 1, 1-11

Abstract: 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.

Date: 2016
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DOI: 10.1038/ncomms12387

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