The 5 kDa protein NdhP is essential for stable NDH-1L assembly in Thermosynechococcus elongatus.

Andrew Webber,Hannes Wulfhorst,Thomas Wessinghage,Linda E Franken,Egbert J Boekema,Marc M Nowaczyk

doi:10.1371/journal.pone.0103584

Andrew Webber, Hannes Wulfhorst + Show 4 more

Open Access

https://doi.org/10.1371/journal.pone.0103584

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Journal: PloS one	Publication Date: Aug 13, 2014
Citations: 60	License type: CC BY 4.0

Affiliation: Ruhr University Bochum, University of Groningen

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.

Highlights

The cyanobacterial and chloroplast type I NADPH dehydrogenase (NDH-1) complex is structurally and functionally related to the energy-converting NAD(P)H:Quinone oxidoreductase (Complex I) – one key-enzyme of the energy metabolism in eubacteria and the respiratory chain of mitochondria [1,2,3]
Cyanobacterial NDH-1 and the closely related chloroplast NDH complex are located in the thylakoid membrane and play a pivotal role in respiration as well as in cyclic electron transfer (CET) around PSI [7,8]
This led to the recent idea that electron transfer via ferredoxin might be a possible pathway to chloroplast NDH and cyanobacterial NDH-1 [11,12]

Summary

Introduction

The cyanobacterial and chloroplast type I NADPH dehydrogenase (NDH-1) complex is structurally and functionally related to the energy-converting NAD(P)H:Quinone oxidoreductase (Complex I) – one key-enzyme of the energy metabolism in eubacteria (like Escherichia coli) and the respiratory chain of mitochondria [1,2,3]. It was previously shown that fusion of several NDH-1 subunits with YFP and the subsequent analysis by electron microscopy and single particle averaging revealed the position of the tagged subunits inside the NDH-1 complex of Synechocystis sp. The complete segregation of the T. elongatus NdhP-sfGFP-His mutant was confirmed by PCR analysis (Fig. 3).

Results

Conclusion