Photosynthesis Research

, Volume 95, Issue 2–3, pp 279–284 | Cite as

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
  • Heidi N. LeBlanc
  • Andrew S. Lang
  • J. Thomas Beatty
Regular Paper

Abstract

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.

Keywords

Photosynthesis Purple bacteria Light-harvesting LH1 LH2 Rhodobacter PucC LhaA Bacteriochlorophyll delivery homologues Complex-specific assembly factors 

Abbreviations

BCD

Bacteriochlorophyll delivery

BChl

Bacteriochlorophyll a

ICM

Intracytoplasmic membrane system

LH1

Light-harvesting complex 1

LH2

Light-harvesting complex 2

RC

Reaction centre

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Copyright information

© Springer Science+Business Media B.V. 2007

Authors and Affiliations

  • Paul R. Jaschke
    • 1
  • Heidi N. LeBlanc
    • 1
    • 2
  • Andrew S. Lang
    • 3
  • J. Thomas Beatty
    • 1
  1. 1.Department of Microbiology and ImmunologyUniversity of British ColumbiaVancouverCanada
  2. 2.Medarex, IncMilpitasUSA
  3. 3.Department of Biology Memorial University of NewfoundlandSt. John’sCanada

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