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Energy coupling efficiency in the Type I ABC transporter GlnPQ

Lycklama A Nijeholt, J. A., Vietrov, R., Schuurman-Wolters, G. K. & Poolman, B., 16-Mar-2018, In : Journal of Molecular Biology. 430, 6, p. 853-866 14 p.

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  • Energy Coupling Efficiency in the Type I ABC Transporter GlnPQ

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DOI

Solute transport via ABC importers involves receptor-mediated substrate binding, which is followed by ATP-driven translocation of the substrate across the membrane. How these steps are exactly initiated and coupled, and how much ATP it takes to complete a full transport cycle, are subject of debate. Here, we reconstitute the ABC importer GlnPQ in nanodiscs and in proteoliposomes and determine substrate-(in)dependent ATP hydrolysis and transmembrane transport. We determined the conformational states of the substrate-binding domains (SBDs) by single-molecule FRET measurements. We find that the basal ATPase activity (ATP hydrolysis in the absence of substrate) is mainly caused by the docking of the closed-unliganded state of the SBDs onto the transporter domain of GlnPQ and that, unlike glutamine, arginine binds both SBDs but does not trigger their closing. Furthermore, comparison of the ATPase activity in nanodiscs with glutamine transport in proteoliposomes shows that the stoichiometry of ATP per substrate is close to two. These findings help understand the mechanism of transport and the energy coupling efficiency in ABC transporters with covalently-linked SBDs, which may aid our understanding of Type I ABC importers in general.

Original languageEnglish
Pages (from-to)853-866
Number of pages14
JournalJournal of Molecular Biology
Volume430
Issue number6
Early online date9-Feb-2018
Publication statusPublished - 16-Mar-2018

    Keywords

  • Membrane transport, ABC importer, Substrate-binding domain, Energy coupling efficiency, TP/substrate stoichiometry, Nanodiscs, Proteoliposomes, SUBSTRATE-BINDING DOMAINS, PHOSPHOLIPID-BILAYER NANODISCS, MALTOSE TRANSPORTER, CONFORMATIONAL DYNAMICS, CASSETTE TRANSPORTER, LACTOCOCCUS-LACTIS, CRYSTAL-STRUCTURE, PERIPLASMIC LOOP, ATP HYDROLYSIS, PROTEIN

ID: 54463437