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Title: Staphylococcus aureus SarA is a Regulatory Protein Responsive to Redox and pH that Can Support Bacteriophage Lambda Integrase Mediated Excision/Recombination

item Higginbotham, Robin
item STERBA, K M - Arkansas State University
item Maleki, Soheila
item SEGALL, A M - San Diego State University
item SMELTZER, M S - Arkansas State University
item Hurlburt, Barry

Submitted to: Molecular Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/24/2009
Publication Date: 11/25/2009
Citation: Fujimoto, D.F., Sterba, K., Segall, A., Maleki, S.J., Higginbotham, R.H., Smeltzer, M., Hurlburt, B.K. 2009. Staphylococcus aureus SarA is a Regulatory Protein Responsive to Redox and pH that Can Support Bacteriophage Lambda Integrase Mediated Excision/Recombination. Molecular Microbiology. 74(6):1445-58.

Interpretive Summary: Staphylococcus aureus is a pathogen that causes matitis in cows and many diseases in humans. The SarA protein has been shown to be important for pathogenesis. Our group and others have shown previously that SarA binds to DNA. In this paper we show that SarA is highly abundant in S. aureus cells. It is capable of binding DNA at all stages of growth. The affinity of SarA for DNA changes depending on the state of reduction/oxidation and pH. Furthermore, we show that SarA should be considered an accessory protein because of its ability to participate in recombination and excision.

Technical Abstract: Staphylococcus aureus produces a wide array of virulence factors that largely come under the control of global regulators. One of these, SarA, has been considered to be a transcription factor, and to regulate over a hundred genes as either a repressor or activator. Here, we show that SarA is present at all stages of growth in vitro and is capable of binding DNA with high affinity. Using competitive ELISA assays, SarA was determined to be present at approximately 50,000 copies per cell, which is not characteristic of classical transcription factors. The binding affinity and pattern of shifted complexes in electrophoretic mobility shift assays were responsive to the redox state. The redox responsiveness is, at least in part, mediated by the lone cysteine residue at position nine. SarA also binds to the bacteriophage ë attachment site, attL, producing SarA-DNA complexes similar to intasomes, which consist of bacteriophage lambda Integrase, E. coli Integration host factor and attL DNA. In addition, SarA stimulates intramolecular excision recombination in the absence of ë Excisionase, a DNA binding accessory protein. These data show that SarA forms organized higher-order protein-DNA complexes and suggests that it can function as an architectural accessory protein stimulating Integrase-mediated recombination.