Photosynthesis Research

, Volume 95, Issue 2, pp 279–284

The PucC protein of Rhodobacter capsulatus mitigates an inhibitory effect of light-harvesting 2 α and β proteins on light-harvesting complex 1


  • Paul R. Jaschke
    • Department of Microbiology and ImmunologyUniversity of British Columbia
  • Heidi N. LeBlanc
    • Department of Microbiology and ImmunologyUniversity of British Columbia
    • Medarex, Inc
  • Andrew S. Lang
    • Department of Biology Memorial University of Newfoundland
    • Department of Microbiology and ImmunologyUniversity of British Columbia
Regular Paper

DOI: 10.1007/s11120-007-9258-x

Cite this article as:
Jaschke, P.R., LeBlanc, H.N., Lang, A.S. et al. Photosynth Res (2008) 95: 279. doi:10.1007/s11120-007-9258-x


Rhodobacter capsulatus contains lhaA and pucC genes that have been implicated in light-harvesting complex 1 and 2 (LH1 and LH2) assembly. The proteins encoded by these genes, and homologues in other photosynthetic organisms, have been classified as the bacteriochlorophyll delivery (BCD) family of the major facilitator superfamily. A new BCD family phylogenetic tree reveals that several PucC, LhaA and Orf428-related sequences each form separate clusters, while plant and cyanobacterial homologues cluster more distantly. The PucC protein is encoded in the pucBACDE superoperon which also codes for LH2 α (PucA) and β (PucB) proteins. PucC was previously shown to be necessary for formation of LH2. This article gives evidence indicating that PucC has a shepherding activity that keeps the homologous α and β proteins of LH1 and LH2 apart, allowing LH1 to assemble properly. This shepherding function was indicated by a 62% reduction in LH1 levels in ΔLHII strains carrying plasmids encoding pucBA along with a C-terminally truncated pucC gene. More severe reductions in LH1 were seen when the truncated pucC gene was co-expressed in the presence of C-terminal PucC::PhoA fusion proteins. It appears that interaction between truncated PucC::PhoA fusion proteins and the truncated PucC protein disrupts LH1 assembly, pointing towards a PucC dimeric or multimeric functional unit.


PhotosynthesisPurple bacteriaLight-harvestingLH1LH2RhodobacterPucCLhaABacteriochlorophyll delivery homologuesComplex-specific assembly factors



Bacteriochlorophyll delivery


Bacteriochlorophyll a


Intracytoplasmic membrane system


Light-harvesting complex 1


Light-harvesting complex 2


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© Springer Science+Business Media B.V. 2007