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Cell. 2018 Jun 14;173(7):1636-1649.e16. doi: 10.1016/j.cell.2018.03.071. Epub 2018 May 10.

Structure of an Ancient Respiratory System.

Author information

1
Cryo-EM Structural Biology Laboratory, Van Andel Research Institute, Grand Rapids, MI 49503, USA.
2
Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA.
3
David Van Andel Advanced Cryo-Electron Microsocpy Suite, Van Andel Research Institute, Grand Rapids, MI, USA.
4
Institute of Biological Chemistry, Washington State University, Pullman, WA 99163, USA.
5
Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA. Electronic address: adamsm@uga.edu.
6
Cryo-EM Structural Biology Laboratory, Van Andel Research Institute, Grand Rapids, MI 49503, USA. Electronic address: huilin.li@vai.org.

Abstract

Hydrogen gas-evolving membrane-bound hydrogenase (MBH) and quinone-reducing complex I are homologous respiratory complexes with a common ancestor, but a structural basis for their evolutionary relationship is lacking. Here, we report the cryo-EM structure of a 14-subunit MBH from the hyperthermophile Pyrococcus furiosus. MBH contains a membrane-anchored hydrogenase module that is highly similar structurally to the quinone-binding Q-module of complex I while its membrane-embedded ion-translocation module can be divided into a H+- and a Na+-translocating unit. The H+-translocating unit is rotated 180° in-membrane with respect to its counterpart in complex I, leading to distinctive architectures for the two respiratory systems despite their largely conserved proton-pumping mechanisms. The Na+-translocating unit, absent in complex I, resembles that found in the Mrp H+/Na+ antiporter and enables hydrogen gas evolution by MBH to establish a Na+ gradient for ATP synthesis near 100°C. MBH also provides insights into Mrp structure and evolution of MBH-based respiratory enzymes.

KEYWORDS:

Mrp antiporter; cation/proton antiporter; complex I; cryo-EM; hydrogen gas; hydrogenase; membrane protein; protein structure; respiration evolution of respiratory complexes; structural biology

PMID:
29754813
PMCID:
PMC6003862
[Available on 2019-06-14]
DOI:
10.1016/j.cell.2018.03.071
[Indexed for MEDLINE]

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