Subunit Q Is Required to Stabilize the Large Complex of NADPH Dehydrogenase in Synechocystis sp. Strain PCC 6803

Abstract

Two major complexes of NADPH dehydrogenase (NDH-1) have been identified in cyanobacteria. A large complex (NDH-1L) contains NdhD1, NdhF1, and NdhP, which are absent in a medium size complex (NDH-1M). They play important roles in respiration, NDH-1-dependent cyclic electron transport around photosystem I, and CO 2 uptake. Two mutants sensitive to high light for growth and impaired in cyclic electron transport around photosystem I were isolated from the cyanobacterium Synechocystis sp. strain PCC 6803 transformed with a transposon-bearing library. Both mutants had a tag in an open reading frame encoding a product highly homologous to NdhQ, a single-transmembrane small subunit of the NDH-1L complex, identified in Thermosynechococcus elongatus by proteomics strategy. Deletion of ndhQ disassembled about one-half of the NDH-1L to NDH-1M and consequently impaired respiration, but not CO 2 uptake. During prolonged incubation of the thylakoid membrane with n-dodecyl-b-D-maltoside at room temperature, the rest of the NDH-1L in DndhQ was disassembled completely to NDH-1M and was much faster than in the wild type. In the ndhP-deletion mutant (DndhP) background, absence of NdhQ almost completely disassembled the NDH-1L to NDH-1M, similar to the results observed in the DndhD1/DndhD2 mutant. We therefore conclude that both NdhQ and NdhP are essential to stabilize the NDH-1L complex.

NdhV Is a Subunit of NADPH Dehydrogenase Essential for Cyclic Electron Transport in Synechocystis sp. Strain PCC 6803

“…This approach has been extensively used to monitor NDH-CET activity in cyanobacteria (Mi et al, 1995;Deng et al, 2003a;Ma and Mi, 2005;Battchikova et al, 2011b;Dai et al, 2013;Zhang et al, 2014;Zhao et al, 2014bZhao et al, , 2015 and higher plants (Burrows et al, 1998;Shikanai et al, 1998;Hashimoto et al, 2003;Wang et al, 2006b;Peng et al, 2009Peng et al, , 2011aPeng et al, , 2012Sirpiö et al, 2009;Yamamoto et al, 2011;Armbruster et al, 2013). As shown in Figure 1B, the NDH-CET activity in both mutants was lower than that in the wild type as judged by the height and relative rate of postillumination increase in Chl fluorescence.…”

“…When AL was turned off after 30-s illumination by AL (800 mmol photons m 2 2 s 2 1 ) supplemented with FR light, P700 + was transiently reduced by electrons from the plastoquinone pool, and subsequently P700 was reoxidized by background FR. Operation of the NDH-1 complexes, which transfer electrons from the reduced cytoplasmic pool to plastoquinone, hinders the reoxidation of P700 (Shikanai et al, 1998;Battchikova et al, 2011b;Dai et al, 2013;Zhang et al, 2014;Zhao et al, 2014bZhao et al, , 2015. The reoxidation of P700 was evidently faster in ΔndhV compared with the wild type but was much slower than in M55 Table S1.…”

“…Glc-tolerant strain of wild-type Synechocystis 6803 and its mutants, ΔndhS (Battchikova et al, 2011b), ΔndhV, ΔndhB (M55; Ogawa, 1991), ΔndhD3/D4 (ΔD3/D4; Ohkawa et al, 2000), and ΔndhQ (Zhao et al, 2015), were cultured at 30°C or 42°C in BG-11 medium (Allen, 1968) buffered with either Tris-HCl (5 mM, pH 8.0) or MES-KOH (20 mM, pH 6.5) by bubbling with 2% (v/v) CO 2 in air or air alone. Solid medium was BG-11 supplemented with 1.5% (w/v) agar.…”

“…Over the past decade, new subunits of NDH-1 complexes specific to oxygenic photosynthesis have been identified in several cyanobacterial strains. They are NdhM to NdhQ and NdhS (Prommeenate et al, 2004;Battchikova et al, 2005Battchikova et al, , 2011bNowaczyk et al, 2011;Wulfhorst et al, 2014;Zhang et al, 2014;Zhao et al, 2014bZhao et al, , 2015, in addition to NdhL first identified in the cyanobacterium Synechocystis sp. strain PCC 6803 (hereafter Synechocystis 6803) about 20 years ago (Ogawa, 1992).…”

Functional characterization of the subunits N, H, J, and O of the NAD(P)H dehydrogenase complexes in Synechocystis sp. strain PCC 6803

“…Nowaczyk et al (2011) reported two novel small subunits, NdhP and NdhQ, which were included in the purified NDH-1L complex by Ni 2+ affinity chromatography and sizeexclusion chromatography from T. elongatus. Recently, it has been demonstrated that NdhP and NdhQ are involved in respiration and CET and are required to stabilize the NDH-1L complex (Schwarz et al, 2013;Wulfhorst et al, 2014;Zhang et al, 2014;Zhao et al, 2015). In recent years, it has been reported that the newly identified OPS subunit, NdhS from Arabidopsis (also known as CRR31) or from Synechocystis 6803 contains Src homology 3 domain-like fold, which serves as the ferredoxin (Fd) docking site domain (Yamamoto et al, 2011;Battchikova et al, 2011b;Yamamoto and Shikanai, 2013), and the authors suggested that the chloroplast NDH complex could accept electrons from Fd rather than NAD(P)H. By studying the purified NDH-1L complex from the thermophilic cyanobacterium T. elongatus, we demonstrated that NDH-1L Figure 1.…”