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Journal of Bacteriology, February 2005, p. 1334-1343, Vol. 187, No. 4
0021-9193/05/$08.00+0     doi:10.1128/JB.187.4.1334-1343.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

The PuhB Protein of Rhodobacter capsulatus Functions in Photosynthetic Reaction Center Assembly with a Secondary Effect on Light-Harvesting Complex 1

Muktak Aklujkar,1 Roger C. Prince,2 and J. Thomas Beatty1*

Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada,1 ExxonMobil Research and Engineering Co., Annandale, New Jersey2

Received 5 September 2004/ Accepted 8 November 2004

The core of the photosynthetic apparatus of purple photosynthetic bacteria such as Rhodobacter capsulatus consists of a reaction center (RC) intimately associated with light-harvesting complex 1 (LH1) and the PufX polypeptide. The abundance of the RC and LH1 components was previously shown to depend on the product of the puhB gene (formerly known as orf214). We report here that disruption of puhB diminishes RC assembly, with an indirect effect on LH1 assembly, and reduces the amount of PufX. Under semiaerobic growth conditions, the core complex was present at a reduced level in puhB mutants. After transfer of semiaerobically grown cultures to photosynthetic (anaerobic illuminated) conditions, the RC/LH1 complex became only slightly more abundant, and the amount of PufX increased as cells began photosynthetic growth. We discovered that the photosynthetic growth of puhB disruption strains of R. capsulatus starts after a long lag period, which is due to physiological adaptation rather than secondary mutations. Using a hybrid protein expression system, we determined that the three predicted transmembrane segments of PuhB are capable of spanning a cell membrane and that the second transmembrane segment could mediate self-association of PuhB. We discuss the possible function of PuhB as a dimeric RC assembly factor.

* Corresponding author. Mailing address: Department of Microbiology and Immunology, University of British Columbia, 300-6174 University Blvd., Vancouver, British Columbia V6T 1Z3, Canada. Phone: (604) 822-6896. Fax: (604) 822-6041. E-mail: jbeatty{at}interchange.ubc.ca.

Journal of Bacteriology, February 2005, p. 1334-1343, Vol. 187, No. 4
0021-9193/05/$08.00+0     doi:10.1128/JB.187.4.1334-1343.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Arai, H., Roh, J. H., Kaplan, S. (2008). Transcriptome Dynamics during the Transition from Anaerobic Photosynthesis to Aerobic Respiration in Rhodobacter sphaeroides 2.4.1. J. Bacteriol. 190: 286-299 [Abstract] [Full Text]  


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