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Journal of Bacteriology, July 2009, p. 4341-4352, Vol. 191, No. 13
0021-9193/09/$08.00+0     doi:10.1128/JB.00243-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Regulation of Gene Expression by PrrA in Rhodobacter sphaeroides 2.4.1: Role of Polyamines and DNA Topology{triangledown}

Jesus M. Eraso and Samuel Kaplan*

Department of Microbiology and Molecular Genetics, University of Texas Health Science Center, Houston, Texas 77030

Received 23 February 2009/ Accepted 22 April 2009

In the present study, we show in vitro binding of PrrA, a global regulator in Rhodobacter sphaeroides 2.4.1, to the PrrA site 2, within the RSP3361 locus. Specific binding, as shown by competition experiments, requires the phosphorylation of PrrA. The binding affinity of PrrA for site 2 was found to increase 4- to 10-fold when spermidine was added to the binding reaction. The presence of extracellular concentrations of spermidine in growing cultures of R. sphaeroides gave rise to a twofold increase in the expression of the photosynthesis genes pucB and pufB, as well as the RSP3361 gene, under aerobic growth conditions, as shown by the use of lacZ transcriptional fusions, and led to the production of light-harvesting spectral complexes. In addition, we show that negative supercoiling positively regulates the expression of the RSP3361 gene, as well as pucB. We show the importance of supercoiling through an evaluation of the regulation of gene expression in situ by supercoiling, in the case of the former gene, as well as using the DNA gyrase inhibitor novobiocin. We propose that polyamines and DNA supercoiling act synergistically to regulate expression of the RSP3361 gene, partly by affecting the affinity of PrrA binding to the PrrA site 2 within the RSP3361 gene.

* Corresponding author. Mailing address: Department of Microbiology and Molecular Genetics, University of Texas Health Center, Houston, TX 77030. Phone: (713) 500-5505. Fax: (713) 500-5499. E-mail: Samuel.Kaplan{at}uth.tmc.edu

{triangledown} Published ahead of print on 1 May 2009.

Journal of Bacteriology, July 2009, p. 4341-4352, Vol. 191, No. 13
0021-9193/09/$08.00+0     doi:10.1128/JB.00243-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Eraso, J. M., Kaplan, S. (2009). Half-Site DNA Sequence and Spacing Length Contributions to PrrA Binding to PrrA Site 2 of RSP3361 in Rhodobacter sphaeroides 2.4.1. J. Bacteriol. 191: 4353-4364 [Abstract] [Full Text]  


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