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Journal of Bacteriology, December 2007, p. 8405-8416, Vol. 189, No. 23
0021-9193/07/$08.00+0     doi:10.1128/JB.01038-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

The Catabolite Control Protein CcpA Binds to Pmga and Influences Expression of the Virulence Regulator Mga in the Group A Streptococcus{triangledown} ,{dagger}

Audry C. Almengor,1,{ddagger} Traci L. Kinkel,1,2,{ddagger} Stephanie J. Day,1 and Kevin S. McIver1,2*

Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9048,1 Department of Cell Biology and Molecular Genetics and Maryland Pathogen Research Institute, University of Maryland, College Park, Maryland 20742-44512

Received 30 June 2007/ Accepted 18 September 2007

Carbon catabolite repression (CCR) allows bacteria to alter metabolism in response to the availability of specific sugar sources, and increasing evidence suggests that CCR is involved in regulating virulence gene expression in many pathogens. A scan of the M1 SF370 group A streptococcus (GAS) genome using a Bacillus subtilis consensus identified a number of potential catabolite-responsive elements (cre) important for binding by the catabolite control protein A (CcpA), a mediator of CCR in gram-positive bacteria. Intriguingly, a putative cre was identified in the promoter region of mga upstream of its distal P1 start of transcription. Electrophoretic mobility shift assays showed that a His-CcpA fusion protein was capable of binding specifically to the cre in Pmga in vitro. Deletion analysis of Pmga using single-copy Pmga-gusA reporter strains found that Pmga P1 and its upstream cre were not required for normal autoregulated mga expression from Pmga P2 as long as Mga was produced from its native locus. In fact, the Pmga P1 region appeared to show a negative influence on Pmga P2 in these studies. However, deletion of the cre at the native Pmga resulted in a reduction of total mga transcripts as determined by real-time reverse transcription-PCR, supporting a role for CcpA in initial expression. Furthermore, normal transcriptional initiation from the Pmga P1 start site alone was dependent on the presence of the cre. Importantly, inactivation of ccpA in the M6 GAS strain JRS4 resulted in a reduction in Pmga expression and Mga protein levels in late-logarithmic-phase cell growth. These data support a role for CcpA in the early activation of the mga promoter and establish a link between CCR and Mga regulation in the GAS.

* Corresponding author. Mailing address: Department of Cell Biology and Molecular Genetics, Maryland Pathogen Research Institute MPRI, University of Maryland, College Park, MD 20742-4451. Phone: (301) 405-4136. Fax: (301) 314-9489. E-mail: kmciver{at}umd.edu

{triangledown} Published ahead of print on 28 September 2007.

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

{ddagger} These authors contributed equally to this work.

Journal of Bacteriology, December 2007, p. 8405-8416, Vol. 189, No. 23
0021-9193/07/$08.00+0     doi:10.1128/JB.01038-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



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