9RYF

Heterodimeric ABC exporter TmrAB (wild type) in ATP-bound outward-facing occluded conformation in the absence of Mg2+

Summary for 9RYF

• Entry DOI: 10.2210/pdb9ryf/pdb
• EMDB information: 54378
• Descriptor: Multidrug resistance ABC transporter ATP-binding and permease protein, Nanobody Nb9F10, ADENOSINE-5'-TRIPHOSPHATE, ... (4 entities in total)
• Functional Keywords: atp-binding cassette protein, abc transporter, membrane protein, heterodimer, exporter, transport protein, atpase
• Biological source: Thermus thermophilus; More
• Total number of polymer chains: 3
• Total formula weight: 150908.02

Authors

Susac, L.,Nocker, C.,Tampe, R. (deposition date: 2025-07-15, release date: 2026-04-08, Last modification date: 2026-04-15)

Primary citation

Nocker, C.,Pecak, M.,Nocker, T.,Fahim, A.,Susac, L.,Tampe, R.
Single-molecule dynamics reveal ATP binding alone powers substrate translocation by an ABC transporter.
Nat Commun, 17:-, 2026

PubMed Abstract: ATP-binding cassette (ABC) transporters are molecular machines involved in diverse physiological processes, including antigen processing by TAP, a key component of adaptive immunity. TAP and its bacterial homolog TmrAB use ATP to translocate peptides across membranes, yet the precise mechanism linking ATP binding to substrate movement remains unclear. Here, we employ a single-molecule FRET sensor to visualize single translocation events by individual ABC transporters and thereby overcome the limitations of ensemble averaging. This approach reveals that substrate transport is driven by a conformational switch from the inward- to the outward-facing state. Using a slow-turnover TmrAB variant, we demonstrate that ATP binding alone, even in the absence of Mg, is sufficient to drive a single round of peptide translocation. Cryo-EM structures of wild-type and slow-turnover TmrAB show that ATP binding induces the outward-facing conformation even without Mg. In wild-type TmrAB, this conformational transition supports a single translocation event, whereas Mg-dependent ATP hydrolysis is required to reset the transporter. These findings establish a direct mechanistic link between ATP binding and substrate translocation at single-molecule resolution and provide insight into the catalytic cycle of ABC transporters.

PubMed: 41916987
DOI: 10.1038/s41467-026-70021-1

Experimental method

ELECTRON MICROSCOPY (3.02 Å)