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-Structure paper
タイトル | A structural framework for unidirectional transport by a bacterial ABC exporter. |
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ジャーナル・号・ページ | Proc Natl Acad Sci U S A, Vol. 117, Issue 32, Page 19228-19236, Year 2020 |
掲載日 | 2020年8月11日 |
著者 | Chengcheng Fan / Jens T Kaiser / Douglas C Rees / |
PubMed 要旨 | 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 ...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. |
リンク | Proc Natl Acad Sci U S A / PubMed:32703810 / PubMed Central |
手法 | EM (単粒子) / X線回折 |
解像度 | 3.03 - 3.88 Å |
構造データ | EMDB-21356, PDB-6vqt: EMDB-21357, PDB-6vqu: PDB-6pam: PDB-6pan: PDB-6pao: PDB-6paq: PDB-6par: |
化合物 | ChemComp-ADP: ChemComp-MG: ChemComp-ATP: ChemComp-ANP: ChemComp-VO4: |
由来 |
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キーワード | TRANSPORT PROTEIN (運搬体タンパク質) / ABC transporter / ABC exporter / ATPase (ATPアーゼ) / membrane protein (膜タンパク質) |