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Infection and Immunity, December 2009, p. 5411-5417, Vol. 77, No. 12
0019-9567/09/$08.00+0     doi:10.1128/IAI.00373-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

A Naturally Occurring Rgg Variant in Serotype M3 Streptococcus pyogenes Does Not Activate speB Expression Due to Altered Specificity of DNA Binding{triangledown}

Kyle V. Kappeler,1 Srivishnupriya Anbalagan,1 Alexander V. Dmitriev,1,2 Emily J. McDowell,1 Melody N. Neely,3 and Michael S. Chaussee1*

Division of Basic Biomedical Sciences, Sanford School of Medicine of the University of South Dakota, Vermillion, South Dakota,1 Department of Molecular Microbiology, Institute of Experimental Medicine, St. Petersburg, Russia,2 Immunology and Microbiology Department, Wayne State University School of Medicine, Detroit, Michigan3

Received 1 April 2009/ Returned for modification 15 May 2009/ Accepted 4 September 2009

The transcriptional regulator Rgg of Streptococcus pyogenes is essential for expression of the secreted cysteine protease SpeB. Although all isolates of S. pyogenes possess the speB gene, not all of them produce the protein in vitro. In a murine model of infection, the absence of SpeB production is associated with invasive disease. We speculated that naturally occurring mutations in rgg, which would also abrogate SpeB production, may be present in invasive isolates of S. pyogenes. Examination of the inferred Rgg sequences available in public databases revealed that the rgg gene in strain MGAS315 (a serotype M3 strain associated with invasive disease) encodes a proline at amino acid position 103 (Rgg103P); in contrast, all other strains encode a serine at this position (Rgg103S). A caseinolytic assay and Western blotting indicated that strain MGAS315 does not produce SpeB in vitro. Gene-swapping experiments showed that the rgg gene of MGAS315 is solely responsible for the lack of SpeB expression. In contrast to Rgg103S, Rgg103P does not bind to the speB promoter in gel shift assays, which correlates with a lack of speB expression. Despite its inability to activate speB expression, Rgg103P retains the ability to bind to DNA upstream of norA and to influence its expression. Overall, this study illustrates how variation at the rgg locus may contribute to the phenotypic diversity of S. pyogenes.

* Corresponding author. Mailing address: Division of Basic Biomedical Sciences, Sanford School of Medicine of the University of South Dakota, Lee Medical Building, 414 East Clark Street, Vermillion, SD 57069-2390. Phone: (605) 677-6681. Fax: (605) 677-6381. E-mail: mchausse{at}usd.edu

{triangledown} Published ahead of print on 14 September 2009.

Editor: J. N. Weiser

Infection and Immunity, December 2009, p. 5411-5417, Vol. 77, No. 12
0019-9567/09/$08.00+0     doi:10.1128/IAI.00373-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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