A single power stroke by ATP binding drives substrate translocation in a heterodimeric ABC transporter

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Abstract

ATP-binding cassette (ABC) transporters constitute the largest family of primary active transporters, responsible for many physiological processes and human maladies. However, the mechanism how chemical energy of ATP facilitates translocation of chemically diverse compounds across membranes is poorly understood. Here, we advance the quantitative mechanistic understanding of the heterodimeric ABC transporter TmrAB, a functional homolog of the transporter associated with antigen processing (TAP) by single-turnover analyses at single-liposome resolution. We reveal that a single conformational switch by ATP binding drives unidirectional substrate translocation. After this power stroke, ATP hydrolysis and phosphate release launch the return to the resting state, which facilitates nucleotide exchange and a new round of substrate binding and translocation. In contrast to hitherto existing steady-state assays, our single-turnover approach uncovers the power stroke in substrate translocation and the tight chemomechanical coupling in these molecular machines.

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All data generated or analysed during this study are included in the manuscript and supporting files. Source data files have been provided for Figures 1, 2, 3, 4, and 5.

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Erich Stefan

Institute of Biochemistry, Biocenter, Goethe-University Frankfurt, Frankfurt, Germany

Competing interests
The authors declare that no competing interests exist.
Susanne Hofmann

Institute of Biochemistry, Biocenter, Goethe-University Frankfurt, Frankfurt, Germany

Competing interests
The authors declare that no competing interests exist.
Robert Tampé

Institute of Biochemistry, Biocenter, Goethe-University Frankfurt, Frankfurt, Germany

For correspondence
tampe@em.uni-frankfurt.de

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-0403-2160

Funding

Deutsche Forschungsgemeinschaft (SFB 807 and Ta157/12-1)

Robert Tampé

European Commission (ERC_Ad 789121)

Robert Tampé

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

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This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.