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Nat Struct Mol Biol. 2015 Jan;22(1):57-64. doi: 10.1038/nsmb.2929. Epub 2014 Dec 8.

Conformational dynamics in substrate-binding domains influences transport in the ABC importer GlnPQ.

Author information

1
1] Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, the Netherlands. [2] Molecular Microscopy Research Group, Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands.
2
Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, the Netherlands.
3
Molecular Microscopy Research Group, Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands.

Abstract

The conformational dynamics in ABC transporters is largely elusive. The ABC importer GlnPQ from Lactococcus lactis has different covalently linked substrate-binding domains (SBDs), thus making it an excellent model system to elucidate the dynamics and role of the SBDs in transport. We demonstrate by single-molecule spectroscopy that the two SBDs intrinsically transit from open to closed ligand-free conformation, and the proteins capture their amino acid ligands via an induced-fit mechanism. High-affinity ligands elicit transitions without changing the closed-state lifetime, whereas low-affinity ligands dramatically shorten it. We show that SBDs in the closed state compete for docking onto the translocator, but remarkably the effect is strongest without ligand. We find that the rate-determining steps depend on the SBD and the amino acid transported. We conclude that the lifetime of the closed conformation controls both SBD docking to the translocator and substrate release.

PMID:
25486304
DOI:
10.1038/nsmb.2929
[Indexed for MEDLINE]

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