Cervin M A, Spiegelman G B
Department of Microbiology and Immunology, University of British Columbia, Vancouver, Canada.
Mol Microbiol. 1999 Jan;31(2):597-607. doi: 10.1046/j.1365-2958.1999.01200.x.
Spo0A is a two-domain response regulator required for the initiation of sporulation in Bacillus subtilis. Spo0A is activated by phosphorylation of its regulatory domain by a multicomponent phosphorelay. To define the role of the regulatory domain in the activation of Spo0A, we have characterized four of the sof mutations in vitro. The sof mutations were identified previously as suppressors of the sporulation-negative phenotype resulting from a deletion of the gene for one of the phosphorelay components, spo0F. Like wild-type Spo0A, the transcription stimulation properties of all of the Sof proteins were dependent upon phosphorylation. Sof mutants from two classes were improved substrates for direct phosphorylation by the KinA sensor kinase, providing an explanation for their suppression properties. Two other Sof proteins showed a phosphorylation-dependent enhancement of the stability of the Sof approximately P-RNA polymerase-DNA complex. One of these mutants, Sof114, increased the stability of the Sof114 approximately P-RNAP-DNA complex without increasing its own affinity for the spoIIG promoter. A comparison of the location of the sof mutations with mutations in CheY suggests that phosphorylation of Spo0A results in the exposure of a region in the regulatory domain that interacts with RNA polymerase, thereby contributing to the signal transduction mechanism.
Spo0A是枯草芽孢杆菌中孢子形成起始所需的一种双结构域应答调节因子。Spo0A通过多组分磷酸化信号转导途径使其调节结构域磷酸化而被激活。为了确定调节结构域在Spo0A激活中的作用，我们在体外对四个sof突变进行了表征。sof突变先前被鉴定为一种磷酸化信号转导组分spo0F基因缺失导致的孢子形成阴性表型的抑制因子。与野生型Spo0A一样，所有Sof蛋白的转录刺激特性都依赖于磷酸化。来自两类的Sof突变体是KinA传感激酶直接磷酸化的更好底物，这解释了它们的抑制特性。另外两种Sof蛋白显示出磷酸化依赖性增强的SofP-RNA聚合酶-DNA复合物的稳定性。其中一个突变体Sof114，增加了Sof114P-RNAP-DNA复合物的稳定性，而没有增加其自身对spoIIG启动子的亲和力。将sof突变的位置与CheY中的突变进行比较表明，Spo0A的磷酸化导致调节结构域中与RNA聚合酶相互作用的区域暴露，从而有助于信号转导机制。
