TY - JOUR
T1 - Identification of protein W, the elusive sixth subunit of the Rhodopseudomonas palustris reaction center-light harvesting 1 core complex
AU - Jackson, Philip J.
AU - Hitchcock, Andrew
AU - Swainsbury, David J.K.
AU - Qian, Pu
AU - Martin, Elizabeth C.
AU - Farmer, David A.
AU - Dickman, Mark J.
AU - Canniffe, Daniel P.
AU - Hunter, C. Neil
N1 - Funding Information:
This work was supported by the European Research Council (Advanced Award 338895 ); the Biotechnology and Biological Sciences Research Council ( BBSRC ) UK (Award numbers BB/M000265/1 , BB/M011151/1 and BB/M012166/1 ); the Photosynthetic Antenna Research Center ( PARC ), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science , Office of Basic Energy Sciences (Award number DE-SC0001035 ); and the European Commission (Marie Skłodowska-Curie Global Fellowship 660652 ).
Publisher Copyright:
© 2017
PY - 2018/2
Y1 - 2018/2
N2 - 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 13 years; 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.
AB - 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 13 years; 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.
KW - Helix W
KW - Photosynthesis
KW - PufX
KW - Reaction center-light harvesting 1 (RC-LH1) core complex
KW - Rhodopseudomonas palustris
KW - RPA4402
UR - http://www.scopus.com/inward/record.url?scp=85034442248&partnerID=8YFLogxK
U2 - 10.1016/j.bbabio.2017.11.001
DO - 10.1016/j.bbabio.2017.11.001
M3 - Article
C2 - 29126780
AN - SCOPUS:85034442248
SN - 0005-2728
VL - 1859
SP - 119
EP - 128
JO - Biochimica Et Biophysica Acta-Bioenergetics
JF - Biochimica Et Biophysica Acta-Bioenergetics
IS - 2
ER -