Presence of a large protein complex containing the ndhK gene product and possessing NADH-specific dehydrogenase activity in thylakoid membranes of higher plant chloroplasts

Sazanov, L.A.; Burrows, Paul A.; Nixon, Peter J.

doi:10.1007/978-94-009-0173-5_395

Cited by 7 publications

(4 citation statements)

References 7 publications

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“…However, genes homologous to those encoding for the nucleotide binding polypeptides of complex I have not been found on the ptDNAs studied so far. Therefore, the NDH must have an NADH binding site as demonstrated recently by Sazanov et al (1995) for higher plant plastidic NDH. It was proposed that this enzyme complex acts in cyclic electron transport around P S I (Friedrich et al 1995) comparable to the situation in cyanobacteria (Mi et al 1995).…”

Section: Discussionmentioning

confidence: 92%

“…The maximal photosynthetic 02 evolution of P. meiringensis grown under the light conditions used here is about 70 #M O2/mg Chl*h (Biichel et al 1988). Measuring the amount of the ndhK gene product on higher plant thylakoids, Sazanov et al (1995) calculated 1 NDH per 100 photosynthetic electron transport chains. It has to be emphasized that the concentrations of NAD(P)H used are in the physiological range normally found in higher plant chloroplasts (Krause and Heber 1976).…”

Section: Discussionmentioning

confidence: 99%

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Kinetic and functional characterization of a membrane-bound NAD(P)H dehydrogenase located in the chloroplasts of Pleurochloris meiringensis (Xanthophyceae)

Seidel-Guyenot¹,

Schwabe²,

Büchel³

1996

Photosynth Res

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Using isolated chloroplasts or purified thylakoids from photoautotrophically grown cells of the chromophytic alga Pleurochloris meiringensis (Xanthophyceae) we were able to demonstrate a membrane bound NAD(P)H dehydrogenase activity. NAD(P)H oxidation was detectable with menadione, coenzyme Q0, decylplastoquinone and decylubiquinone as acceptors in an in vitro assay. K m-values for both pyridine nucleotides were in the μmolar range (K m[NADH]=9.8 μM, K m[NADPH]=3.2 μM calculated according to Lineweaver-Burk). NADH oxidation was optimal at pH 9 while pH dependence of NADPH oxidation showed a main peak at 9.8 and a smaller optimum at pH 7.5-8. NADH oxidation could be completely inhibited with rotenone, an inhibitor of mitochondrial complex I dehydrogenase, while NADPH oxidation revealed the typical inhibition pattern upon addition of oxidized pyridine nucleotides reported for ferredoxin: NADP(+) reductase. Partly-denaturing gel electrophoresis followed by NAD(P)H dehydrogenase activity staining showed that NADPH and NADH oxidizing proteins had different electrophoretic mobilities. As revealed by denaturing electrophoresis, the NADH oxidizing enzyme had one main subunit of 22 kDa and two further polypeptides of 29 and 44 kDa, whereas separation of the NADPH depending protein yielded five bands of different molecular weight. Measurement of oxygen consumption due to PS I mediated methylviologen reduction upon complete inhibition of PS II showed that the NAD(P)H dehydrogenase is able to catalyze an input of electrons from NADH to the photosynthetic electron transport chain in case of an oxidized plastoquinone-pool. We suggest ferredoxin: NADP(+) reductase to be the main NADPH oxidizing activity while a thylakoidal NAD(P)H: plastoquinone oxidoreductase involved in the chlororespiratory pathway in the dark acts mainly as an NADH oxidizing enzyme.

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Section: Discussionmentioning

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Kinetic and functional characterization of a membrane-bound NAD(P)H dehydrogenase located in the chloroplasts of Pleurochloris meiringensis (Xanthophyceae)

Seidel-Guyenot¹,

Schwabe²,

Büchel³

1996

Photosynth Res

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“…This would involve the transfer of electrons from NADPH to plastoquinone. The observation that a complex homologous to the mitochondrial NADH dehydrogenase (ndh; complex I) exists in the chloroplast provides a possible mediator for this pathway (Shinokazi et al, 1986;Sazanov et al, 1995). There is some evidence that the ndh complex can mediate a cyclic electron flow in vivo, but concentrations of this enzyme are extremely low so it remains unclear if this flux would ever be significant under physiological conditions (Sazanov et al, 1998;Joet et al, 2002).…”

Section: The Pathway Of Cetmentioning

confidence: 99%

Cyclic electron transport in C3 plants: fact or artefact?

Johnson

2004

Journal of Experimental Botany

148

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The phenomenon of cyclic electron transport was first characterized in higher plant chloroplasts 50 years ago, yet there is still a debate about whether or not this is a physiological process. The recent isolation of mutants that appear to lack cyclic electron transport, as well as new data providing functional evidence for its occurrence, support the notion that this pathway plays an important role in plant responses to stress, providing a pH gradient across the thylakoid membrane to trigger non-photochemical quenching of chlorophyll fluorescence. At present, little is known about the regulation of cyclic electron transport, but it is possible that this is activated in response to a low redox potential in the chloroplast stroma.

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“…Such proton-coupled LEF is still insufficient to support the necessary N3ATP/2NADPH ratio requiring N14H + /4e − [5], therefore, PQ is also reduced by two kinds of cyclic electron flow around PSI (CEF I ), returning to PQ a fraction of electrons once passed through the Cyt b 6 f complex. The (minor) chloroplast NAD(P)H dehydrogenaserelated route of PQ reduction was suggested by [6] and a novel protein component CRR31 is essential for the efficient operation of Fddependent plastoquinone reduction by this complex [7]. The (major) antimycin A-sensitive, ferredoxin-dependent PQ reduction pathway [8] is based on a PROTON GRADIENT REGULATION protein PGR5 [9,10].…”

Section: Introductionmentioning

confidence: 99%

Oxidation of plastohydroquinone by photosystem II and by dioxygen in leaves

Laisk

Eichelmann

Oja

2015

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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In sunflower leaves linear electron flow LEF=4O2 evolution rate was measured at 20 ppm O2 in N2. PSII charge separation rate CSRII=aII∙PAD∙(Fm-F)/Fm, where aII is excitation partitioning to PSII, PAD is photon absorption density, Fm and F are maximum and actual fluorescence yields. Under 630 nm LED+720 nm far-red light (FRL), LEF was equal to CSRII with aII=0.51 to 0.58. After FRL was turned off, plastoquinol (PQH2) accumulated, but LEF decreased more than accountable by F increase, indicating PQH2-oxidizing cyclic electron flow in PSII (CEFII). CEFII was faster under conditions requiring more ATP, consistent with CEFII being coupled with proton translocation. We propose that PQH2 bound to the QC site is oxidized, one e- moving to P680+, the other e- to Cyt b559. From Cyt b559 the e- reduces QB- at the QB site, forming PQH2. About 10-15% electrons may cycle, causing misses in the period-4 flash O2 evolution and lower quantum yield of photosynthesis under stress. We also measured concentration dependence of PQH2 oxidation by dioxygen, as indicated by post-illumination decrease of Chl fluorescence yield. After light was turned off, F rapidly decreased from Fm to 0.2 Fv, but further decrease to F0 was slow and O2 concentration dependent. The rate constant of PQH2 oxidation, determined from this slow phase, was 0.054 s(-1) at 270 μM (21%) O2, decreasing with Km(O2) of 60 μM (4.6%) O2. This eliminates the interference of O2 in the measurements of CEFII.

show abstract

Presence of a large protein complex containing the ndhK gene product and possessing NADH-specific dehydrogenase activity in thylakoid membranes of higher plant chloroplasts

Cited by 7 publications

References 7 publications

Kinetic and functional characterization of a membrane-bound NAD(P)H dehydrogenase located in the chloroplasts of Pleurochloris meiringensis (Xanthophyceae)

Kinetic and functional characterization of a membrane-bound NAD(P)H dehydrogenase located in the chloroplasts of Pleurochloris meiringensis (Xanthophyceae)

Cyclic electron transport in C3 plants: fact or artefact?

Oxidation of plastohydroquinone by photosystem II and by dioxygen in leaves

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