Regulation of gene expression by PrrA in Rhodobacter sphaeroides 2.4.1: role of polyamines and DNA topology.
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.
Department of Microbiology and Molecular Genetics, University of Texas Health Science Center, Houston, Texas 77030, USA.
Jesus M
JM
Eraso
Samuel
S
Kaplan
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001483:Base Sequence; D004269:DNA, Bacterial / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects / Q000235:genetics; D008969:Molecular Sequence Data; D009675:Novobiocin / Q000494:pharmacology; D009690:Nucleic Acid Conformation / Q000187:drug effects; D010766:Phosphorylation; D010788:Photosynthesis / Q000235:genetics / Q000502:physiology; D011073:Polyamines / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D012242:Rhodobacter sphaeroides / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D013095:Spermidine / Q000494:pharmacology; D059005:Topoisomerase II Inhibitors
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D011073:Polyamines; D059005:Topoisomerase II Inhibitors; D009675:Novobiocin; D013095:Spermidine