Identification of protein W, the elusive sixth subunit of the Rhodopseudomonas palustris reaction center-light harvesting 1 core complex



Jackson, Philip J, Hitchcock, Andrew, Swainsbury, David JK, Qian, Pu, Martin, Elizabeth C, Farmer, David A, Dicknan, Mark J, Canniffe, Daniel P ORCID: 0000-0002-5022-0437 and Hunter, C Neil
(2018) Identification of protein W, the elusive sixth subunit of the Rhodopseudomonas palustris reaction center-light harvesting 1 core complex. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS, 1859 (2). pp. 119-128.

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Abstract

The X-ray crystal structure of the Rhodopseudomonas (Rps.) palustris reaction center-light harvesting 1 (RC-LH1) core complex revealed the presence of a sixth protein component, variably referred to in the literature as helix W, subunit W or protein W. The position of this protein prevents closure of the LH1 ring, possibly to allow diffusion of ubiquinone/ubiquinol between the RC and the cytochrome bc<sub>1</sub> complex in analogous fashion to the well-studied PufX protein from Rhodobacter sphaeroides. The identity and function of helix W have remained unknown for over 13years; here we use a combination of biochemistry, mass spectrometry, molecular genetics and electron microscopy to identify this protein as RPA4402 in Rps. palustris CGA009. Protein W shares key conserved sequence features with PufX homologs, and although a deletion mutant was able to grow under photosynthetic conditions with no discernible phenotype, we show that a tagged version of protein W pulls down the RC-LH1 complex. Protein W is not encoded in the photosynthesis gene cluster and our data indicate that only approximately 10% of wild-type Rps. palustris core complexes contain this non-essential subunit; functional and evolutionary consequences of this observation are discussed. The ability to purify uniform RC-LH1 and RC-LH1-protein W preparations will also be beneficial for future structural studies of these bacterial core complexes.

Item Type: Article
Uncontrolled Keywords: Photosynthesis, Rhodopseudomonas palustris, Reaction center-light harvesting 1 (RC-LH1), core complex, Helix W, RPA4402, PufX
Depositing User: Symplectic Admin
Date Deposited: 31 May 2019 07:57
Last Modified: 19 Jan 2023 00:42
DOI: 10.1016/j.bbabio.2017.11.001
Open Access URL: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC57641...
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URI: https://livrepository.liverpool.ac.uk/id/eprint/3043786

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