Photosynthesis Research

, Volume 88, Issue 2, pp 159–171

Investigation of Rhodobacter capsulatus PufX interactions in the core complex of the photosynthetic apparatus

Regular paper


The photosynthetic apparatus of purple bacteria in the genus Rhodobacter includes a core complex consisting of the reaction centre (RC), light-harvesting complex 1 (LH1), and the PufX protein. PufX modulates LH1 structure and facilitates photosynthetic quinone/quinol exchange. We deleted RC/LH1 genes in pufX+ and pufX++ (merodiploid) strains of Rhodobacter capsulatus, which reduced PufX levels regardless of pufX gene copy number and location. Photosynthetic growth of RC-only strains and independent assembly kinetics of the RC and LH1 were unaffected by pufX merodiploidy, but the absorption spectra of strains expressing the RC plus either LH1 α or β indicated that PufX may influence bacteriochlorophyll binding environments. Significant self-association of the PufX transmembrane segment was detected in a hybrid protein expression system, consistent with a role of PufX in core complex dimerization, as proposed for other Rhodobacter species. Our results indicate that in R. capsulatus PufX has the potential to be a central, homodimeric core complex component, and its cellular level is increased by interactions with the RC and LH1.


bacteriochlorophyll light-harvesting photosynthesis PufX purple bacteria reaction centre Rhodobacter TOXCAT 



bacteriochlorophyll a


bacteriopheophytin a

cyt b/c1

cytochrome b/c1 complex


light-harvesting complex 1


light-harvesting complex 2


intracytoplasmic membrane system


reaction centre


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Abresch EC, Axelrod HLA, Beatty JT, Johnson JA, Nechushtai R, Paddock ML (2005) Characterization of a highly purified, fully active, crystallizable RC–LH1–PufX core complex from Rhodobacter sphaeroides Photosynth Res 86: 61-70PubMedCrossRefGoogle Scholar
  2. Aklujkar M, Beatty JT (2005) The PufX protein of Rhodobacter capsulatus affects the properties of bacteriochlorophyll a and carotenoid pigments of light-harvesting complex 1Arch Biochem Biophys 443: 21–32PubMedCrossRefGoogle Scholar
  3. Aklujkar M, Harmer AL, Prince RC, Beatty JT (2000) The orf162b sequence of Rhodobacter capsulatus encodes a protein required for optimal levels of photosynthetic pigment–protein complexes J Bacteriol 182: 5440–5447PubMedCrossRefGoogle Scholar
  4. Aklujkar M, Prince RC, Beatty JT (2005a) The PuhB protein of Rhodobacter capsulatus functions in photosynthetic reaction centre assembly with a secondary effect on light-harvesting complex 1J Bacteriol 187: 1334–1343CrossRefGoogle Scholar
  5. Aklujkar M, Prince RC, Beatty JT (2005b) The puhE gene of Rhodobacter capsulatus is needed for optimal transition from aerobic to photosynthetic growth and encodes a putative negative modulator of bacteriochlorophyll production Arch Biochem Biophys 437: 186–198CrossRefGoogle Scholar
  6. Alberti M, Burke DE, Hearst JE (1995) Structure and sequence of the photosynthetic gene cluster. In: Blankenship RE, Madigan MT, Bauer CE (eds) Anoxygenic Photosynthetic Bacteria Kluwer Academic Publishers, Dordrecht, The Netherlands pp. 1083–1106Google Scholar
  7. Bahatyrova S, Frese RN, Siebert CA, Olsen JD, van der Werf KO, van Grondelle R, Niederman RA, Bullough PA, Otto C, Hunter CN (2004) The native architecture of a photosynthetic membrane Nature 430: 1058–1062PubMedCrossRefGoogle Scholar
  8. Barz WP, Francia F, Venturoli G, Melandri BA, Verméglio A, Oesterhelt D (1995a) Role of PufX protein in photosynthetic growth of Rhodobacter sphaeroides. 1. PufX is required for efficient light-driven electron transfer and photophosphorylation under anaerobic conditionsBiochemistry 34: 15235–15247CrossRefGoogle Scholar
  9. Barz WP, Verméglio A, Francia F, Venturoli G, Melandri BA, Oesterhelt D (1995b) Role of PufX protein in photosynthetic growth of Rhodobacter sphaeroides. 2. PufX is required for efficient ubiquinone/ubiquinol exchange between the reaction center QB site and the cytochrome bc 1 complex Biochemistry 34: 15248–15258CrossRefGoogle Scholar
  10. Beatty JT, Gest H (1981) Generation of succinyl-coenzyme A in photosynthetic bacteria Arch Microbiol 129: 335–340CrossRefGoogle Scholar
  11. Bibb MJ, Cohen SN (1982) Gene expression in Streptomyces: construction and application of promoter-probe plasmid vectors in Streptomyces lividans Mol Gen Genet 187: 265–277PubMedCrossRefGoogle Scholar
  12. Comayras F, Jungas C, Lavergne J (2005a) Functional consequences of the organization of the photosynthetic apparatus in Rhodobacter sphaeroides. I. Quinone domains and excitation transfer in chromatophores and reaction center antenna complexes J Biol Chem 280: 11203–11213CrossRefGoogle Scholar
  13. Comayras F, Jungas C, Lavergne J (2005b) Functional consequences of the organization of the photosynthetic apparatus in Rhodobacter sphaeroides. II. A study of PufX membranes J Biol Chem 280: 11214–11223CrossRefGoogle Scholar
  14. Ditta G, Schmidhauser T, Yakobsen E, Lu P, Liang X-W, Finlay DR, Guiney D, Helinski DR (1985) Plasmids related to the broad host range vector, pRK290, useful for gene cloning and for monitoring gene expression Plasmid 13: 149–153PubMedCrossRefGoogle Scholar
  15. Drews G, Golecki JR (1995) Structure, molecular organization, and biosynthesis of membranes of purple bacteria. In: Blankenship RE, Madigan MT, Bauer CE (eds) Anoxygenic Photosynthetic Bacteria Kluwer Academic Publishers, Dordrecht, The Netherlands 231–257Google Scholar
  16. Farchaus JW, Barz WP, Grünberg H, Oesterhelt D (1992) Studies on the expression of the pufX polypeptide and its requirement for photoheterotrophic growth in Rhodobacter sphaeroides EMBO J 11: 2779–2788PubMedGoogle Scholar
  17. Feick R, van Grondelle R, Rijgersberg CP, Drews G (1980) Fluorescence emission by wild-type and mutant strains of Rhodopseudomonas capsulata Biochim Biophys Acta 593: 241–253PubMedCrossRefGoogle Scholar
  18. Francia F, Dezi M, Rebecchi A, Mallardi A, Palazzo G, Melandri BA, Venturoli G (2004) Light-harvesting complex 1 stabilizes P+QB charge separation in reaction centers of Rhodobacter sphaeroides Biochemistry 43: 14199–14210PubMedCrossRefGoogle Scholar
  19. Francia F, Wang J, Venturoli G, Melandri BA, Barz WP, Oesterhelt D (1999) The reaction center-LH1 antenna complex of Rhodobacter sphaeroides contains one PufX molecule which is involved in dimerization of this complex Biochemistry 38: 6834–6845PubMedCrossRefGoogle Scholar
  20. Francia F, Wang J, Zischka H, Venturoli G, Oesterhelt D (2002) Role of the N- and C-terminal regions of the PufX protein in the structural organization of the photosynthetic core complex of Rhodobacter sphaeroidesEur J Biochem 269: 1877–1885PubMedCrossRefGoogle Scholar
  21. Frese RN, Olsen JD, Branvall R, Westerhuis WHJ, Hunter CN, van Grondelle R (2000) The long-range supraorganization of the bacterial photosynthetic unit: a key role for PufX Proc Natl Acad Sci USA 97: 5197–5202PubMedCrossRefGoogle Scholar
  22. Goldsmith JO, King B, Boxer SG (1996) Mg coordination by amino acid side chains is not required for assembly and function of the special pair in bacterial photosynthetic reaction centers Biochemistry 35: 2421–2428PubMedCrossRefGoogle Scholar
  23. Jackson WJ, Kiley PJ, Haith CE, Kaplan S, Prince RC (1987) On the role of the light-harvesting B880 in the correct insertion of the reaction center of Rhodobacter capsulatus and Rhodobacter sphaeroides FEBS Lett 215: 171–174PubMedCrossRefGoogle Scholar
  24. Joliot P, Joliot A, Verméglio A (2005) Fast oxidation of the primary electron acceptor under anaerobic conditions requires the organization of the photosynthetic chain of Rhodobacter sphaeroides in supercomplexes Biochim Biophys Acta 1706: 204–214PubMedCrossRefGoogle Scholar
  25. Jones MR, Fowler GJS, Gibson LCD, Grief GG, Olsen JD, Crielaard W, Hunter CN (1992) Mutants of Rhodobacter sphaeroides lacking one or more pigment–protein complexes and complementation with reaction-centre, LH1, and LH2 genes Mol Microbiol 6(9): 1173–1184PubMedCrossRefGoogle Scholar
  26. Jungas C, Ranck J-L, Rigaud J-L, Joliot P, Verméglio A (1999) Supramolecular organization of the photosynthetic apparatus of Rhodobacter sphaeroides EMBO J 18: 534–542PubMedCrossRefGoogle Scholar
  27. Klug G, Cohen SN (1988) Pleiotropic effects of localized Rhodobacter capsulatus puf operon deletions on production of light-absorbing pigment–protein complexesJ Bacteriol 170: 5814–5821PubMedGoogle Scholar
  28. Law CJ, Chen J, Parkes-Loach PS, Loach PA (2003) Interaction of bacteriochlorophyll with the LH1 and PufX polypeptides of photosynthetic bacteria: use of chemically synthesized analogs and covalently attached fluorescent probes Photosynth Res 75: 193–210PubMedCrossRefGoogle Scholar
  29. LeBlanc H, Lang AS, Beatty JT (1999) Transcript cleavage, attenuation and an internal promoter in the Rhodobacter capsulatus puc operonJ Bacteriol 181: 4955–4960PubMedGoogle Scholar
  30. Lilburn TG, Haith CE, Prince RC, Beatty JT (1992) Pleiotropic effects of pufX gene deletion on the structure and function of the photosynthetic apparatus of Rhodobacter capsulatus Biochim Biophys Acta 1100: 160–170PubMedCrossRefGoogle Scholar
  31. Lilburn TG, Prince RC, Beatty JT (1995) Mutation of the Ser2 codon of the light-harvesting B870 α polypeptide of Rhodobacter capsulatus partially suppresses the pufX phenotype J Bacteriol 177: 4593–4600PubMedGoogle Scholar
  32. McGlynn P, Hunter CN, Jones MR (1994) The Rhodobacter sphaeroides PufX protein is not required for photosynthetic competence in the absence of a light harvesting system FEBS Lett 349: 349–353PubMedCrossRefGoogle Scholar
  33. Papiz MZ, Prince SM, Hawthornthwaite-Lawless AM, McDermott G, Freer AA, Isaacs NW, Cogdell RJ (1996) A model for the photosynthetic apparatus of purple bacteria Trends Plant Sci 1: 198–206CrossRefGoogle Scholar
  34. Parkes -Loach PS, Law CJ, Recchia PA, Kehoe J, Nehrlich S, Chen J, Loach PA (2001) Role of the core region of the PufX protein in inhibition of reconstitution of the core light-harvesting complexes of Rhodobacter sphaeroides and Rhodobacter capsulatus Biochemistry 40: 5593–5601PubMedCrossRefGoogle Scholar
  35. Pugh RJ, McGlynn P, Jones MR, Hunter CN (1998) The LH1-RC core complex of Rhodobacter sphaeroides: interaction between components, time-dependent assembly, and topology of the PufX proteinBiochim Biophys Acta 1366: 301–316PubMedCrossRefGoogle Scholar
  36. Qian P, Hunter CN, Bullough PA (2005) The 8.5 Å projection structure of the core RC–LH1–PufX dimer of Rhodobacter sphaeroidesJ Mol Biol 349: 948–960PubMedCrossRefGoogle Scholar
  37. Recchia PA, Davis CM, Lilburn TG, Beatty JT, Parkes-Loach PS, Hunter CN, Loach PA (1998) Isolation of the PufX protein from Rhodobacter capsulatus and Rhodobacter sphaeroides: evidence for its interaction with the α-polypeptide of the core light harvesting complex Biochemistry 37: 11055–11063PubMedCrossRefGoogle Scholar
  38. Richter P, Drews G (1991) Incorporation of light-harvesting complex I α and β polypeptides into the intracytoplasmic membrane of Rhodobacter capsulatus J Bacteriol 173: 5336–5345PubMedGoogle Scholar
  39. Russ WP, Engelman DM (1999) TOXCAT: a measure of transmembrane helix association in a biological membrane Proc Natl Acad Sci USA 96: 863–868PubMedCrossRefGoogle Scholar
  40. Sambrook J, Fritsch EF, Maniatis T (1989) Molecular Cloning: A Laboratory Manual Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.YGoogle Scholar
  41. Scheuring S, Busselez J, Lévy D (2005) Structure of the dimeric PufX-containing core complex of Rhodobacter blasticus by in situ AFM J Biol Chem 280: 1426–1431PubMedCrossRefGoogle Scholar
  42. Scheuring S, Francia F, Busselez J, Melandri BA, Rigaud J-L, Lévy D (2004) Structural role of PufX in the dimerization of the photosynthetic core complex of Rhodobacter sphaeroides J Biol Chem 279: 3620–3626PubMedCrossRefGoogle Scholar
  43. Scolnik PA, Marrs BL (1987) Genetic research with photosynthetic bacteria Annu Rev of Microbiol 41: 703–726CrossRefGoogle Scholar
  44. Siebert CA, Qian P, Fotiadis D, Engel A, Hunter CN, Bullough PA (2004) Molecular architecture of photosynthetic membranes in Rhodobacter sphaeroides: the role of PufX EMBO J 23: 690–700PubMedCrossRefGoogle Scholar
  45. Solioz M, Marrs B (1977) The gene transfer agent of Rhodopseudomonas capsulata Arch Biochem Biophys 181: 300–307PubMedCrossRefGoogle Scholar
  46. Tsukatani Y, Matsuura K, Masuda S, Shimada K, Hiraishi A, Nagashima KVP (2004) Phylogenetic distribution of unusual triheme to tetraheme cytochrome subunit in the reaction center complex of purple photosynthetic bacteria Photosynth Res 79: 83–91PubMedCrossRefGoogle Scholar
  47. Waidner LA, Kirchman DL (2005) Aerobic anoxygenic photosynthesis genes and operons in uncultured bacteria in the Delaware River Environ Microbiol 7: 1896–1908PubMedCrossRefGoogle Scholar
  48. Westerhuis WHJ, Farchaus JW, Niederman RA (1993) Altered spectral properties of the B875 light-harvesting pigment–protein complex in a Rhodobacter sphaeroides mutant lacking pufX Photochem Photobiol 58: 460–463CrossRefGoogle Scholar
  49. Young CS, Reyes RC, Beatty JT (1998) Genetic complementation and kinetic analyses of Rhodobacter capsulatus ORF1696 mutants indicate that the ORF1696 protein enhances assembly of the light-harvesting I complex J Bacteriol 180: 1759–1765PubMedGoogle Scholar
  50. Youvan DC, Ismail S, Bylina EJ (1985) Chromosomal deletion and plasmid complementation of the photosynthetic reaction center and light harvesting genes from Rhodopseudomonas capsulataGene 38: 19–30PubMedCrossRefGoogle Scholar
  51. Yutin N, Béjà O (2005) Putative novel photosynthetic reaction centre organizations in marine aerobic anoxygenic photosynthetic bacteria: insights from metagenomics and environmental genomics Environ Microbiol 7: 2027–2033PubMedCrossRefGoogle Scholar
  52. Zilsel J, Lilburn T, Beatty JT (1989) Formation of functional inter-species hybrid photosynthetic complexes in Rhodobacter capsulatus FEBS Lett 253: 247–252PubMedCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, Inc. 2006

Authors and Affiliations

  1. 1.Department of Microbiology and ImmunologyUniversity of British ColumbiaVancouverCanada
  2. 2.Department of MicrobiologyUniversity of Massachusetts AmherstAmherstUSA

Personalised recommendations