title: The 5 kDa protein NdhP is essential for stable NDH-1L assembly in Thermosynechococcus elongatus.
abstract: The cyanobacterial NADPH:plastoquinone oxidoreductase complex (NDH-1), that is related to Complex I of eubacteria and mitochondria, plays a pivotal role in respiration as well as in cyclic electron transfer (CET) around PSI and is involved in a unique carbon concentration mechanism (CCM). Despite many achievements in the past, the complex protein composition and the specific function of many subunits of the different NDH-1 species remain elusive. We have recently discovered in a NDH-1 preparation from Thermosynechococcus elongatus two novel single transmembrane peptides (NdhP, NdhQ) with molecular weights below 5 kDa. Here we show that NdhP is a unique component of the ∼ 450 kDa NDH-1L complex, that is involved in respiration and CET at high CO2 concentration, and not detectable in the NDH-1MS and NDH-1MS' complexes that play a role in carbon concentration. C-terminal fusion of NdhP with his-tagged superfolder GFP and the subsequent analysis of the purified complex by electron microscopy and single particle averaging revealed its localization in the NDH-1L specific distal unit of the NDH-1 complex, that is formed by the subunits NdhD1 and NdhF1. Moreover, NdhP is essential for NDH-1L formation, as this type of NDH-1 was not detectable in a ΔndhP::Km mutant.
authors.affiliation: Department of Plant Biochemistry, Ruhr-University Bochum, Bochum, Germany.
authors.forename: Hannes
authors.initials: H
authors.lastname: Wulfhorst
authors.affiliation: Electron Microscopy Department, University of Groningen, Groningen, The Netherlands.
authors.forename: Linda E
authors.initials: LE
authors.lastname: Franken
authors.affiliation: Department of Plant Biochemistry, Ruhr-University Bochum, Bochum, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Wessinghage
authors.affiliation: Electron Microscopy Department, University of Groningen, Groningen, The Netherlands.
authors.forename: Egbert J
authors.initials: EJ
authors.lastname: Boekema
authors.affiliation: Department of Plant Biochemistry, Ruhr-University Bochum, Bochum, Germany.
authors.forename: Marc M
authors.initials: MM
authors.lastname: Nowaczyk
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D019069:Cell Respiration; D000458:Cyanobacteria / Q000235:genetics / Q000378:metabolism*; D004579:Electron Transport; D008958:Models, Molecular; D009247:NADH, NADPH Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000235:genetics / Q000502:physiology; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein
chemical_list: D001426:Bacterial Proteins; D021122:Protein Subunits; D009247:NADH, NADPH Oxidoreductases; C072396:NAD(P)H plastoquinone oxidoreductase