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

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 bc1 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.

SUBMITTER: Jackson PJ

PROVIDER: S-EPMC5764122 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature

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

Jackson Philip J PJ Hitchcock Andrew A Swainsbury David J K DJK Qian Pu P Martin Elizabeth C EC Farmer David A DA Dickman Mark J MJ Canniffe Daniel P DP Hunter C Neil CN

Biochimica et biophysica acta. Bioenergetics 20171107 2

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 spha ...[more]

PMID: 29126780

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Project description:Peripheral light harvesting (LH) antenna complexes have been studied extensively in the purple nonsulfur bacterium Rhodopseudomonas palustris because it produces different types of LH complexes under high light intensities (LH2 complex) and low light intensities (LH3 and LH4 complex). The ability of R. palustris to alter its peripheral LH complexes in response to changes in light intensity is attributed to the multiple operons that encode the a and b peptides that make up these complexes, whose expression is affected by light intensity, light quality, and oxygen tension. However, low resolution structures, amino acid similarities between the complexes, and a lack of transcriptional analysis made it difficult to determine the LH complexes composition and functions under different light intensities. It was also unclear how much diversity of the R. palustris LH complexes exists in nature.Results: To gain insight into the composition of the LH complexes, their function under high light intensities and low light intensities, and their prevalence in the environment we undertook an integrative genomics approach using 15 closely related R. palustris strains isolated from the environment and 5 R. palustris ecotypes whose genomes have been sequenced. We sequenced the genomes for the 15 closely related strains and using RNA-seq carried out transcriptomic analysis on all 20 strains grown under high light intensity and low light intensity. We were able to determine that even closely related R. palustris strains had differences in their pucBA gene content and expression, even under the same growth conditions. We also found that the LH2 complex could compensate for the lack of an LH4 complex under LL intensities but not under extremely LL intensities. Conclusions: This is the first time an integrative genomics approach has been used to study light harvesting in the environment. The variation observed in LH gene composition and expression in environmental isolates of R. palustris likely reflects how these strains have adapted to specific light conditions in the environment. We have also shown that there is redundancy between some of the LH complexes under certain light intensities, which may partially explain why multiple operons encoding LH complexes have evolved and been maintained in R. palustris.

Dataset Information

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

Publications

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

Similar Datasets

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