This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Nygaard, P. Articles by Saxild, H. H. Search for Related Content PubMed PubMed Citation Articles by Nygaard, P. Articles by Saxild, H. H.

The Purine Efflux Pump PbuE in Bacillus subtilis Modulates Expression of the PurR and G-Box (XptR) Regulons by Adjusting the Purine Base Pool Size

Institute of Molecular Biology, Department of Biological Chemistry, University of Copenhagen, Copenhagen,¹ BioCentrum-DTU, Technical University of Denmark, Lyngby, Denmark²

Received 9 July 2004/ Accepted 4 October 2004

In Bacillus subtilis, the expression of genes encoding enzymes and other proteins involved in purine de novo synthesis and salvage is affected by purine bases and phosphoribosylpyrophosphate (PRPP). The transcription of the genes belonging to the PurR regulon is negatively regulated by the PurR protein and PRPP. The expression of the genes belonging to the G-box (XptR) regulon, including the pbuE gene, is negatively regulated by a riboswitch-controlled transcription termination mechanism. The G-box regulon effector molecules are hypoxanthine and guanine. pbuE encodes a purine base efflux pump and is now recognized as belonging to a third purine regulon. The expression of the pbuE gene is positively regulated by a riboswitch that recognizes adenine. Here we show that the expression of pbuE'-lacZ transcriptional fusions are induced by adenine to the highest extent in mutants which do not express a functional PbuE pump. In a mutant defective in the metabolism of adenine, the ade apt mutant, we found a high intracellular level of adenine and constitutive high levels of PbuE. A growth test using a purine auxotroph provided further evidence for the role of PbuE in lowering the intracellular concentration of purine bases, including adenine. Purine analogs also affect the expression of pbuE, which might be of importance for the protection against toxic analogs. In a mutant that overexpresses PbuE, the expression of genes belonging to the PurR regulon was increased. Our findings provide further evidence for important functions of the PbuE protein, such as acting as a pump that lowers the purine base pool and affects the expression of the G-box and PurR regulons, including pbuE itself, and as a pump involved in protection against toxic purine base analogs.

This article has been cited by other articles:

• Ganas, P., Mihasan, M., Igloi, G. L., Brandsch, R. (2007). A two-component small multidrug resistance pump functions as a metabolic valve during nicotine catabolism by Arthrobacter nicotinovorans. Microbiology 153: 1546-1555 [Abstract] [Full Text]  
• Lemay, J.-F., Lafontaine, D. A. (2007). Core requirements of the adenine riboswitch aptamer for ligand binding. RNA 13: 339-350 [Abstract] [Full Text]  
• Schyns, G., Potot, S., Geng, Y., Barbosa, T. M., Henriques, A., Perkins, J. B. (2005). Isolation and Characterization of New Thiamine-Deregulated Mutants of Bacillus subtilis. J. Bacteriol. 187: 8127-8136 [Abstract] [Full Text]