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Role of RsbU in controlling SigB activity in Staphylococcus aureus following alkaline stress

Lookup NU author(s): Steven Hardwick, Professor Rick Lewis

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Abstract

SigB is an alternative sigma factor that controls a large regulon in Staphylococcus aureus. Activation of SigB requires RsbU, a protein phosphatase 2C (PP2C)-type phosphatase. In a closely related organism, Bacillus subtilis, RsbU activity is stimulated upon interaction with RsbT, a kinase, which following an activating stimulus switches from a 25S high-molecular-weight complex, the stressosome, to the N-terminal domain of RsbU. Active RsbU dephosporylates RsbV and thereby triggers the release of SigB from its inhibitory complex with RsbW. While RsbU, RsbV, RsbW, and SigB are conserved in S. aureus, proteins similar to RsbT and the components of the stressosome are not, raising the question of how RsbU activity and hence SigB activity are controlled in S. aureus. We found that in contrast to the case in B. subtilis, the induced expression of RsbU was sufficient to stimulate SigB-dependent transcription in S. aureus. However, activation of SigB-dependent transcription following alkaline stress did not lead to a clear accumulation of SigB and its regulators RsbV and RsbW or to a change in the RsbV/RsbV-P ratio in S. aureus. When expressed in B. subtilis, the S. aureus RsbU displayed a high activity even in the absence of an inducing stimulus. This high activity could be transferred to the PP2C domain of the B. subtilis RsbU protein by a fusion to the N-terminal domain of the S. aureus RsbU. Collectively, the data suggest that the activity of the S. aureus RsbU and hence SigB may be subjected to different regulation in comparison to that in B. subtilis.

Publication metadata

Author(s): Pane-Farre J, Jonas B, Hardwick SW, Gronau K, Lewis RJ, Hecker M, Engelmann S

Publication type: Article

Publication status: Published

Journal: Journal of Bacteriology

Year: 2009

Volume: 191

Issue: 8

Pages: 2561-2573

ISSN (print): 0021-9193

ISSN (electronic): 1098-5530

Publisher: American Society for Microbiology

URL: http://dx.doi.org/10.1128/JB.01514-08

DOI: 10.1128/JB.01514-08

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