To investigate the (co)expression, interaction, and membrane location of multifunctional NAD(P)H dehydrogenase type 1 (NDH-1) complexes and their involvement in carbon acquisition, cyclic photosystem I, and respiration, we grew the wild type and specific ndh gene knockout mutants of Synechocystis sp PCC 6803 under different CO 2 and pH conditions, followed by a proteome analysis of their membrane protein complexes. Typical NDH-1 complexes were represented by NDH-1L (large) and NDH-1M (medium size), located in the thylakoid membrane. The NDH-1L complex, missing from the DNdhD1/D2 mutant, was a prerequisite for photoheterotrophic growth and thus apparently involved in cellular respiration. The amount of NDH-1M and the rate of P700 þ rereduction in darkness in the DNdhD1/D2 mutant grown at low CO 2 were similar to those in the wild type, whereas in the M55 mutant (DNdhB), lacking both NDH-1L and NDH-1M, the rate of P700 þ rereduction was very slow. The NDH-1S (small) complex, localized to the thylakoid membrane and composed of only NdhD3, NdhF3, CupA, and Sll1735, was strongly induced at low CO 2 in the wild type as well as in DNdhD1/D2 and M55. In contrast with the wild type and DNdhD1/D2, which show normal CO 2 uptake, M55 is unable to take up CO 2 even when the NDH-1S complex is present. Conversely, the DNdhD3/D4 mutant, also unable to take up CO 2 , lacked NDH-1S but exhibited wild-type levels of NDH-1M at low CO 2 . These results demonstrate that both NDH-1S and NDH-1M are essential for CO 2 uptake and that NDH-1M is a functional complex. We also show that the Na þ /HCO 3 ÿ transporter (SbtA complex) is located in the plasma membrane and is strongly induced in the wild type and mutants at low CO 2 .

Cyanobacterial NDH-1 complexes belong to a family of energy converting NAD(P)H:Quinone oxidoreductases that includes bacterial type-I NADH dehydrogenase and mitochondrial Complex I. Several distinct NDH-1 complexes may coexist in cyanobacterial cells and thus be responsible for a variety of functions including respiration, cyclic electron flow around PSI and CO(2) uptake. The present review is focused on specific features that allow to regard the cyanobacterial NDH-1 complexes, together with NDH complexes from chloroplasts, as a separate sub-class of the Complex I family of enzymes. Here, we summarize our current knowledge about structure of functionally different NDH-1 complexes in cyanobacteria and consider implications for a functional mechanism. This article is part of a Special Issue entitled: Regulation of Electron Transport in Chloroplasts.

The composition and dynamics of membrane protein complexes were studied in the cyanobacterium Synechocystis sp. PCC 6803 by two-dimensional blue native/SDS-PAGE followed by matrix-assisted laser-desorption ionization time of flight mass spectrometry. Approximately 20 distinct membrane protein complexes could be resolved from photoautotrophically grown wild-type cells. Besides the protein complexes involved in linear photosynthetic electron flow and ATP synthesis (photosystem [PS] I, PSII, cytochrome b 6 f, and ATP synthase), four distinct complexes containing type I NAD(P)H dehydrogenase (NDH-1) subunits were identified, as well as several novel, still uncharacterized protein complexes. The dynamics of the protein complexes was studied by culturing the wild type and several mutant strains under various growth modes (photoautotrophic, mixotrophic, or photoheterotrophic) or in the presence of different concentrations of CO 2 , iron, or salt. The most distinct modulation observed in PSs occurred in iron-depleted conditions, which induced an accumulation of CP43Ј protein associated with PSI trimers. The NDH-1 complexes, on the other hand, responded readily to changes in the CO 2 concentration and the growth mode of the cells and represented an extremely dynamic group of membrane protein complexes. Our results give the first direct evidence, to our knowledge, that the NdhF3, NdhD3, and CupA proteins assemble together to form a small low CO 2 -induced protein complex and further demonstrate the presence of a fourth subunit, Sll1735, in this complex. The two bigger NDH-1 complexes contained a different set of NDH-1 polypeptides and are likely to function in respiratory and cyclic electron transfer. Pulse labeling experiments demonstrated the requirement of PSII activity for de novo synthesis of the NDH-1 complexes.Photosynthetic organisms experience continuous fluctuation in their growth environment, including changes in light conditions, temperature, and nutrient availability. Cyanobacteria, the probable progenitors of chloroplasts, possess a remarkable capacity to adapt to a wide range of environmental conditions. Cyanobacteria are primarily photoautotrophic, but some strains, such as Synechocystis sp. PCC 6803, can also grow mixotrophically or photoheterotrophically in the presence of external Glc. This, together with their flexibility to genetic manipulation and simple nutrient requirements for growth, has rendered cyanobacteria into a favored model in deciphering the structurefunction relationships and acclimation strategies of the photosynthetic machinery.Energy-transducing thylakoid membranes are the targets for modification by a number of environmental variables. Light, the most important environmental factor for photosynthesis, induces a well-defined acclimation response, including changes in the amount and ratio of the two PSs (Fujita, 1997;Hihara, 1999) and in the abundance and composition of the light-harvesting phycobilisome antenna (Grossman et al., 1993(Grossman et al., , 2001. Similar responses in th...

Viral genomes often contain genes recently acquired from microbes. In some cases (for example, psbA) the proteins encoded by these genes have been shown to be important for viral replication. In this study, using a unique search strategy on the Global Ocean Survey (GOS) metagenomes in combination with marine virome and microbiome pyrosequencing-based datasets, we characterize previously undetected microbial metabolic capabilities concealed within the genomes of uncultured marine viral communities. A total of 34 microbial gene families were detected on 452 viral GOS scaffolds. The majority of auxiliary metabolic genes found on these scaffolds have never been reported in phages. Host genes detected in viruses were mainly divided between genes encoding for different energy metabolism pathways, such as electron transport and newly identified photosystem genes, or translation and post-translation mechanism related. Our findings suggest previously undetected ways, in which marine phages adapt to their hosts and improve their fitness, including translation and post-translation level control over the host rather than the already known transcription level control.

To study the synthesis and assembly of multisubunit thylakoid protein complexes, we performed [35S]Met pulse and chase experiments with isolated chloroplasts and intact leaves of spinach (Spinacia oleracea L.), followed by Blue Native gel separation of the (sub)complexes and subsequent identification of the newly synthesized and assembled protein subunits. PSII (photosystem II) core subunits were the most intensively synthesized proteins, particularly in vitro and at high light intensities in vivo, and could be sequestered in several distinct PSII subassemblies. Newly synthesized D1 was first found in the reaction centre complex that also contained labelled D2 and two labelled low-molecular-mass proteins. The next biggest PSII subassembly contained CP47 also. Then PsbH was assembled together with at least two other labelled chloroplast-encoded low-molecular-mass subunits, PsbM and PsbTc, and a nuclear-encoded PsbR. Subsequently, CP43 was inserted into the PSII complex concomitantly with PsbK. These assembly steps seemed to be essential for the dimerization of PSII core monomers. Intact PSII core monomer was the smallest subcomplex harbouring the newly synthesized 33 kDa oxygen-evolving complex protein PsbO. Nuclear-encoded PsbW was synthesized only at low light intensities concomitantly with Lhcb polypeptides and was distinctively present in PSII-LHCII (where LHC stands for light-harvesting complex) supercomplexes. The PsbH protein, on the contrary, was vigorously synthesized and incorporated into PSII core monomers together with the D1 protein, suggesting an intrinsic role for PsbH in the photoinhibition-repair cycle of PSII.