The 5 kDa Protein NdhP Is Essential for Stable NDH-1L Assembly in Thermosynechococcus elongatus
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| Authors: | Hannes Wulfhorst Linda E Franken Thomas Wessinghage Egbert J Boekema Marc M Nowaczyk |
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| Institution: | 1. Department of Plant Biochemistry, Ruhr-University Bochum, Bochum, Germany.; 2. Electron Microscopy Department, University of Groningen, Groningen, The Netherlands.; Arizona State University, United States of America, |
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| 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. |
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