6VQU

Structure of a bacterial Atm1-family ABC exporter

Summary for 6VQU

• Entry DOI: 10.2210/pdb6vqu/pdb
• Related: 6PAM 6PAN 6PAO 6PAQ 6PAR
• EMDB information: 21357
• Descriptor: ATM1-type heavy metal exporter (1 entity in total)
• Functional Keywords: abc transporter, membrane protein, transport protein
• Biological source: Novosphingobium aromaticivorans (strain ATCC 700278 / DSM 12444 / CIP 105152 / NBRC 16084 / F199)
• Total number of polymer chains: 2
• Total formula weight: 135543.20

Authors

Fan, C.,Rees, D.C. (deposition date: 2020-02-05, release date: 2020-07-29, Last modification date: 2024-03-06)

Primary citation

Fan, C.,Kaiser, J.T.,Rees, D.C.
A structural framework for unidirectional transport by a bacterial ABC exporter.
Proc.Natl.Acad.Sci.USA, 117:19228-19236, 2020

PubMed Abstract: The ATP-binding cassette (ABC) transporter of mitochondria (Atm1) mediates iron homeostasis in eukaryotes, while the prokaryotic homolog from (Atm1) can export glutathione derivatives and confer protection against heavy-metal toxicity. To establish the structural framework underlying the Atm1 transport mechanism, we determined eight structures by X-ray crystallography and single-particle cryo-electron microscopy in distinct conformational states, stabilized by individual disulfide crosslinks and nucleotides. As Atm1 progresses through the transport cycle, conformational changes in transmembrane helix 6 (TM6) alter the glutathione-binding site and the associated substrate-binding cavity. Significantly, kinking of TM6 in the post-ATP hydrolysis state stabilized by MgADPVO eliminates this cavity, precluding uptake of glutathione derivatives. The presence of this cavity during the transition from the inward-facing to outward-facing conformational states, and its absence in the reverse direction, thereby provide an elegant and conceptually simple mechanism for enforcing the export directionality of transport by Atm1. One of the disulfide crosslinked Atm1 variants characterized in this work retains significant glutathione transport activity, suggesting that ATP hydrolysis and substrate transport by Atm1 may involve a limited set of conformational states with minimal separation of the nucleotide-binding domains in the inward-facing conformation.

PubMed: 32703810
DOI: 10.1073/pnas.2006526117

Experimental method

ELECTRON MICROSCOPY (3.88 Å)