This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Supplemental material
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by de la Riva, L.
Right arrow Articles by Baldoma, L.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by de la Riva, L.
Right arrow Articles by Baldoma, L.

 Previous Article  |  Next Article 

Journal of Bacteriology, December 2008, p. 7892-7903, Vol. 190, No. 24
0021-9193/08/$08.00+0     doi:10.1128/JB.01022-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

The hpx Genetic System for Hypoxanthine Assimilation as a Nitrogen Source in Klebsiella pneumoniae: Gene Organization and Transcriptional Regulation{triangledown} ,{dagger}

Lucia de la Riva,1 Josefa Badia,1 Juan Aguilar,1* Robert A. Bender,2 and Laura Baldoma1

Departament de Bioquímica i Biología Molecular, Institut de Biomedicina de la Universitat de Barcelona, Facultat de Farmacia, Universitat de Barcelona, E-08028 Barcelona, Spain,1 Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan2

Received 24 July 2008/ Accepted 29 September 2008

Growth experiments showed that adenine and hypoxanthine can be used as nitrogen sources by several strains of K. pneumoniae under aerobic conditions. The assimilation of all nitrogens from these purines indicates that the catabolic pathway is complete and proceeds past allantoin. Here we identify the genetic system responsible for the oxidation of hypoxanthine to allantoin in K. pneumoniae. The hpx cluster consists of seven genes, for which an organization in four transcriptional units, hpxDE, hpxR, hpxO, and hpxPQT, is proposed. The proteins involved in the oxidation of hypoxanthine (HpxDE) or uric acid (HpxO) did not display any similarity to other reported enzymes known to catalyze these reactions but instead are similar to oxygenases acting on aromatic compounds. Expression of the hpx system is activated by nitrogen limitation and by the presence of specific substrates, with hpxDE and hpxPQT controlled by both signals. Nitrogen control of hpxPQT transcription, which depends on {sigma}54, is mediated by the Ntr system. In contrast, neither NtrC nor the nitrogen assimilation control protein is involved in the nitrogen control of hpxDE, which is dependent on {sigma}70 for transcription. Activation of these operons by the specific substrates is also mediated by different effectors and regulatory proteins. Induction of hpxPQT requires uric acid formation, whereas expression of hpxDE is induced by the presence of hypoxanthine through the regulatory protein HpxR. This LysR-type regulator binds to a TCTGC-N4-GCAAA site in the intergenic hpxD-hpxR region. When bound to this site for hpxDE activation, HpxR negatively controls its own transcription.

* Corresponding author. Mailing address: Departament de Bioquímica i Biología Molecular, Facultat de Farmacia, Universitat de Barcelona, Av. Diagonal, 643, E-08028-Barcelona, Spain. Phone: 34-934034496. Fax: 34-934024520. E-mail: juanaguilar{at}ub.edu

{triangledown} Published ahead of print on 10 October 2008.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

Journal of Bacteriology, December 2008, p. 7892-7903, Vol. 190, No. 24
0021-9193/08/$08.00+0     doi:10.1128/JB.01022-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Yu, C. L., Louie, T. M., Summers, R., Kale, Y., Gopishetty, S., Subramanian, M. (2009). Two Distinct Pathways for Metabolism of Theophylline and Caffeine Are Coexpressed in Pseudomonas putida CBB5. J. Bacteriol. 191: 4624-4632 [Abstract] [Full Text]  
  • Pope, S. D., Chen, L.-L., Stewart, V. (2009). Purine Utilization by Klebsiella oxytoca M5al: Genes for Ring-Oxidizing and -Opening Enzymes. J. Bacteriol. 191: 1006-1017 [Abstract] [Full Text]  


Copyright © 2009 by the American Society for Microbiology.   For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»