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Journal of Bacteriology, February 2003, p. 1229-1235, Vol. 185, No. 4
0021-9193/03/$08.00+0     DOI: 10.1128/JB.185.4.1229-1235.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

QscR, a LysR-Type Transcriptional Regulator and CbbR Homolog, Is Involved in Regulation of the Serine Cycle Genes in Methylobacterium extorquens AM1

Marina G. Kalyuzhnaya1 and Mary E. Lidstrom1,2*

Department of Chemical Engineering,1 Department of Microbiology, University of Washington, Seattle, Washington 98195-17502

Received 18 July 2002/ Accepted 24 November 2002

A new gene, qscR, encoding a LysR-type transcriptional regulator that is a homolog of CbbR, has been characterized from the facultative methylotroph Methylobacterium extorquens AM1 and shown to be the major regulator of the serine cycle, the specific C1 assimilation pathway. The qscR mutant was shown to be unable to grow on C1 compounds, and it lacked the activity of serine-glyoxylate aminotransferase, a key enzyme of the serine cycle. Activities of other serine cycle enzymes were decreased during growth on C1 compounds compared to the activities found in wild-type M. extorquens AM1. Promoter fusion assays, as well as reverse transcription-PCR assays, have indicated that the serine cycle genes belong to three separate transcriptional units, sga-hpr-mtdA-fch, mtkA-mtkB-ppc-mcl, and gly. Gel retardation assays involving the purified QscR have demonstrated the specific binding of QscR to the DNA regions upstream of sga, mtkA, gly, and qscR. We conclude that QscR acts as a positive transcriptional regulator of most of the serine cycle enzymes and also as an autorepressor.

* Corresponding author. Mailing address: Department of Chemical Engineering, University of Washington, Seattle, WA 98195-1750. Phone: (206) 616-5282. Fax: (206) 616-5721. E-mail: lidstrom{at}u.washington.edu.

Journal of Bacteriology, February 2003, p. 1229-1235, Vol. 185, No. 4
0021-9193/03/$08.00+0     DOI: 10.1128/JB.185.4.1229-1235.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Strovas, T. J., Lidstrom, M. E. (2009). Population heterogeneity in Methylobacterium extorquens AM1. Microbiology 155: 2040-2048 [Abstract] [Full Text]  
  • Crowther, G. J., Kosaly, G., Lidstrom, M. E. (2008). Formate as the Main Branch Point for Methylotrophic Metabolism in Methylobacterium extorquens AM1. J. Bacteriol. 190: 5057-5062 [Abstract] [Full Text]  
  • Kalyuzhnaya, M. G., Lidstrom, M. E. (2005). QscR-Mediated Transcriptional Activation of Serine Cycle Genes in Methylobacterium extorquens AM1. J. Bacteriol. 187: 7511-7517 [Abstract] [Full Text]  
  • Chistoserdova, L., Chen, S.-W., Lapidus, A., Lidstrom, M. E. (2003). Methylotrophy in Methylobacterium extorquens AM1 from a Genomic Point of View. J. Bacteriol. 185: 2980-2987 [Full Text]  


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