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Structure of NDH the complex I-like molecule of oxygenic photosynthesis

ABSTRACT: Cyclic electron flow (CEF) around photosystem I (PSI) is a mechanism by which photosynthetic organisms balance levels of ATP and NADPH necessary for efficient photosynthesis1,2. The NAD(P)H dehydrogenase-like complex (NDH) is a key component of this pathway in most oxygenic photosynthetic organisms3,4 and the last large photosynthetic membrane protein complex of unknown structure. Related to the respiratory NADH dehydrogenase complex (complex I), NDH transfers electrons originating from PSI to the plastoquinone (PQ) pool, while pumping protons across the thylakoid membrane, thereby increasing the amount of ATP produced per NADP+ molecule reduced4,5. NDH possesses 11 of the 14 core complex I subunits as well as several oxygenic photosynthesis specific (OPS) subunits, which are conserved from cyanobacteria to higher plants3,6. However, the three complex I core subunits involved in accepting electrons from NAD(P)H are notably absent in NDH3,5,6. Thus, how NDH acquires and transfers electrons to PQ is presently unclear. Nevertheless, the OPS subunits, specifically NdhS, are proposed to enable NDH to accept electrons from ferredoxin (Fd), its electron donor3–5,7. Here we report a 3.1 Å structure of the ~0.42 MDa NDH complex from the thermophilic cyanobacterium Thermosynechoccous elongatus BP-1 (T. elongatus) obtained by single-particle cryo-electron microscopy (cryo-EM). Our maps reveal the structure and arrangement of the principle OPS subunits in the NDH complex, as well as an unexpected cofactor near the PQ-binding site in the peripheral arm. The location of the OPS subunits supports a role in electron transfer and defines two potential Fd-binding sites at the apex of the peripheral arm. Together, these results suggest multiple electron transfer routes could be present in NDH, which would serve to maximize PQ reduction and avoid deleterious off-target chemistry of the semi-plastoquinone radical.

INSTRUMENT(S): impact II

ORGANISM(S): Thermosynechococcus Elongatus Bp-1

SUBMITTER: Andrew Bayne

LAB HEAD: Jean-Francois Trempe

PROVIDER: PXD012206 | Pride | 2019-02-18

REPOSITORIES: Pride

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Structure of the complex I-like molecule NDH of oxygenic photosynthesis.

Laughlin Thomas G TG Bayne Andrew N AN Trempe Jean-François JF Savage David F DF Davies Karen M KM

Nature 20190211 7744

Cyclic electron flow around photosystem I (PSI) is a mechanism by which photosynthetic organisms balance the levels of ATP and NADPH necessary for efficient photosynthesis<sup>1,2</sup>. NAD(P)H dehydrogenase-like complex (NDH) is a key component of this pathway in most oxygenic photosynthetic organisms<sup>3,4</sup> and is the last large photosynthetic membrane-protein complex for which the structure remains unknown. Related to the respiratory NADH dehydrogenase complex (complex I), NDH transfe ...[more]

PMID: 30742075

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Project description:Hydrogen can be an important source of energy for chemolithotrophic acidophiles, especially in the deep terrestrial subsurface. Nevertheless, the current knowledge of microbial hydrogen utilization in acidic environments is minimal. A multi-omics analysis was applied on Acidithiobacillus ferrooxidans growing aerobically and anaerobically (with ferric iron) on hydrogen as an electron donor, and a respiratory model proposed from the results obtained. In this model, both [NiFe] hydrogenases, cytoplasmic uptake and membrane-bound respiratory, oxidize molecular hydrogen to two protons and two electrons. The electrons are used to reduce membrane-soluble ubiquinone to ubiquinol. Genetically associated [FeS]-binding proteins mediate electron relay from the hydrogenases to the ubiquinone pool. Under aerobic conditions, reduced ubiquinol transfers electrons to either cytochrome aa3 oxidase via cytochrome bc1 complex and cytochrome c4 or the alternate directly to cytochrome bd oxidase, resulting in proton efflux together with the reduction of molecular oxygen to water. Under anaerobic conditions, reduced ubiquinol transfers electrons to outer membrane cytochrome c (ferric iron reductase) via cytochrome bc1 complex and a cascade of electron transporters (cytochrome c4, cytochrome c552, rusticyanin, and high potential iron-sulfur protein), resulting in proton efflux together with the reduction of ferric iron to ferrous iron. The proton gradient generated by molecular hydrogen oxidation maintains the membrane potential and allows the generation of ATP via ATP synthase and NADH via NADH-ubiquinone oxidoreductase. To a lesser extent, NADH can also be generated by another bidirectional cytoplasmic hydrogenase. ATP and NADH are further utilized in the Calvin–Benson–Bassham cycle for inorganic carbon uptake and assimilation. These results further clarify the role of extremophiles in biogeochemical processes and their impact on the composition and features of the deep terrestrial subsurface from the distant past to the present.

Dataset Information

Structure of NDH the complex I-like molecule of oxygenic photosynthesis

Publications

Structure of the complex I-like molecule NDH of oxygenic photosynthesis.

Similar Datasets

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