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

DOI: 10.1007/s11120-006-9047-y

Cite this article as:
Aklujkar, M. & Beatty, J.T. Photosynth Res (2006) 88: 159. doi:10.1007/s11120-006-9047-y


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.


bacteriochlorophylllight-harvestingphotosynthesisPufXpurple bacteriareaction centreRhodobacterTOXCAT



bacteriochlorophyll a


bacteriopheophytin a

cyt b/c1

cytochrome b/c1 complex


light-harvesting complex 1


light-harvesting complex 2


intracytoplasmic membrane system


reaction centre

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