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Science. 2019 Jan 18;363(6424):257-260. doi: 10.1126/science.aau3613. Epub 2018 Dec 20.

Structural adaptations of photosynthetic complex I enable ferredoxin-dependent electron transfer.

Author information

1
Department of Structural Cell Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany. janschu@biochem.mpg.de gkurisu@protein.osaka-u.ac.jp marc.m.nowaczyk@rub.de.
2
Max Planck Institute for Chemical Energy Conversion, 45470 Mülheim an der Ruhr, Germany.
3
Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan.
4
Department of Macromolecular Science, Graduate School of Science, Osaka University, Toyonaka 560-0043, Japan.
5
Graduate School of Medical Life Science, Yokohama City University, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan.
6
Plant Biochemistry, Faculty of Biology and Biotechnology, Ruhr University Bochum, 44780 Bochum, Germany.
7
Daiichi Sankyo Deutschland GmbH, Zielstattstr. 48, 81379 München, Germany.
8
Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia.
9
Gene Center and Department of Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Str. 25, 81377 Munich, Germany.
10
Institut de Biologie Intégrative de la Cellule (I2BC), IBITECS, CEA, CNRS, Université Paris-Saclay, F-91198 Gif-sur-Yvette, France.
11
Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany.
12
Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan. janschu@biochem.mpg.de gkurisu@protein.osaka-u.ac.jp marc.m.nowaczyk@rub.de.
13
Plant Biochemistry, Faculty of Biology and Biotechnology, Ruhr University Bochum, 44780 Bochum, Germany. janschu@biochem.mpg.de gkurisu@protein.osaka-u.ac.jp marc.m.nowaczyk@rub.de.

Abstract

Photosynthetic complex I enables cyclic electron flow around photosystem I, a regulatory mechanism for photosynthetic energy conversion. We report a 3.3-angstrom-resolution cryo-electron microscopy structure of photosynthetic complex I from the cyanobacterium Thermosynechococcus elongatus. The model reveals structural adaptations that facilitate binding and electron transfer from the photosynthetic electron carrier ferredoxin. By mimicking cyclic electron flow with isolated components in vitro, we demonstrate that ferredoxin directly mediates electron transfer between photosystem I and complex I, instead of using intermediates such as NADPH (the reduced form of nicotinamide adenine dinucleotide phosphate). A large rate constant for association of ferredoxin to complex I indicates efficient recognition, with the protein subunit NdhS being the key component in this process.

PMID:
30573545
DOI:
10.1126/science.aau3613

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