The Bacillus subtilis sigma(X) protein is an extracytoplasmic function sigma factor contributing to survival at high temperature
The Bacillus subtilis sigma(X) protein is an extracytoplasmic function sigma factor contributing to survival at high temperature
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DOI：
10.1128/jb.179.9.2915-2921.1997
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发表时间：
1997-05-01
影响因子：
3.2
通讯作者：
Helmann, JD
中科院分区：
文献类型：
--
作者：
Huang, XJ;Decatur, A;Helmann, JD
作为对枯草芽孢杆菌基因组进行测序的国际合作项目的一部分而被鉴定出的sigX基因，被认为编码一种胞外功能（ECF）亚家族的替代σ因子。在生长的对数期和稳定期早期，sigX基因与下游的ypuN基因共转录。我们现在报道，缺乏σ(X)的菌株在高温下的生存能力受损，而ypuN突变体的耐热性增强。我们在大肠杆菌中过量表达并纯化了σ(X)，并证明在体外，σ(A)和σ(X)全酶都能识别sigX - ypuN调控区内的启动子元件。然而，它们具有不同的最适盐浓度，使得在低盐浓度下σ(A)依赖的转录占主导，而在高盐浓度下σ(X)依赖的转录占主导。sigX上游的一个54bp区域在体内足以作为一个σ(X)依赖的启动子，这表明sigX至少部分处于正的自我调控之下。ypuN的突变增加了体内σ(X)依赖启动子的表达，这表明ypuN可能编码一种σ(X)活性的负调控因子。
The sigX gene, identified as part of the international effort to sequence the Bacillus subtilis genome, has been proposed to encode an alternative a factor of the extracytoplasmic function (ECF) subfamily, The sigX gene is cotranscribed with a downstream gene, ypuN, during logarithmic and early stationary phases of growth, We now report that strains lacking sigma(X) are impaired in the ability to survive at high temperature whereas a ypuN mutant has increased thermotolerance. We overproduced and purified sigma(X) from Escherichia coli and demonstrate that in vitro, both sigma(A) and sigma(X) holoenzymes recognize promoter elements within the sigX-ypuN control region, However, they have distinct salt optima such that sigma(A)-dependent transcription predominates at low salt while ax-dependent transcription predominates at high salt, A 54-bp region upstream of sigX suffices as a ox-dependent promoter in vivo, demonstrating that sigX is at least partially under positive autoregulatory control, Mutation of ypuN increases expression from the ox-dependent promoter in vivo, suggesting that ypuN may encode a negative regulator of sigma(X) activity.