Pané-Farré Jan, Jonas Beate, Hardwick Steven W, Gronau Katrin, Lewis Richard J, Hecker Michael, Engelmann Susanne
Institut für Mikrobiologie, Ernst-Moritz-Arndt-Universität, F.-L.-Jahn-Str. 15, D-17487 Greifswald, Germany.
J Bacteriol. 2009 Apr;191(8):2561-73. doi: 10.1128/JB.01514-08. Epub 2009 Feb 6.
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.
SigB是一种替代的σ因子，可控制金黄色葡萄球菌中的一个大型调控子。SigB的激活需要RsbU，一种蛋白磷酸酶2C（PP2C）型磷酸酶。在一种密切相关的生物体枯草芽孢杆菌中，RsbU与激酶RsbT相互作用时活性会受到刺激，RsbT在激活刺激后会从25S高分子量复合物应激体转变为RsbU的N端结构域。活性RsbU使RsbV去磷酸化，从而触发SigB从其与RsbW的抑制复合物中释放出来。虽然RsbU、RsbV、RsbW和SigB在金黄色葡萄球菌中是保守的，但与RsbT及应激体成分相似的蛋白质却不存在，这就引发了一个问题，即金黄色葡萄球菌中RsbU的活性以及SigB的活性是如何被调控的。我们发现，与枯草芽孢杆菌的情况不同，RsbU的诱导表达足以刺激金黄色葡萄球菌中SigB依赖的转录。然而，碱性应激后SigB依赖的转录激活并未导致金黄色葡萄球菌中SigB及其调节因子RsbV和RsbW的明显积累，也未导致RsbV/RsbV-P比值的变化。当在枯草芽孢杆菌中表达时，金黄色葡萄球菌的RsbU即使在没有诱导刺激的情况下也表现出高活性。通过与金黄色葡萄球菌RsbU的N端结构域融合，这种高活性可以转移到枯草芽孢杆菌RsbU蛋白的PP2C结构域。总体而言，这些数据表明，与枯草芽孢杆菌相比，金黄色葡萄球菌中RsbU的活性以及SigB的活性可能受到不同的调控。
