Identification and functional analysis of novel (p)ppGpp synthetase genes in Bacillus subtilis
Identification and functional analysis of novel (p)ppGpp synthetase genes in Bacillus subtilis
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DOI：
10.1111/j.1365-2958.2007.06018.x
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发表时间：
2008-01-01
影响因子：
3.6
通讯作者：
Tozawa, Yuzuru
中科院分区：
文献类型：
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作者：
Nanamiya, Hideaki;Kasai, Koji;Tozawa, Yuzuru
细菌报警素(p)ppGpp，是全球监管机构负责严格控制的。两种同源 (p)ppGpp 合成酶 RelA 和 SpoT 已在大肠杆菌中得到鉴定和表征，而革兰氏阳性细菌（如枯草芽孢杆菌）被认为仅具有单一的 RelA-SpoT 酶。我们现已在枯草芽孢杆菌中鉴定出两个基因 yjbM 和 ywaC，它们编码一种新型警报酮合成酶。这些基因的预测产物是相对较小的蛋白质（类似于 25 kDa），对应于 RelA-SpoT 家族成员的 (p)ppGpp 合成酶结构域。数据库调查显示，与 yjbM 和 ywaC 同源的基因在属于厚壁菌门或放线菌门的某些细菌中保守，但在变形菌门等其他门中不保守。我们将这些蛋白质命名为小警报素合成酶 (SAS)，以将其与 RelA-SpoT 蛋白质区分开来。通过遗传互补分析和体外酶活性测定证实了 YjbM 和 YwaC 的 (p)ppGpp 合成酶功能。分子遗传学分析还表明，ywaC是由碱激诱导的，导致ppGpp的瞬时积累。因此，SAS 蛋白可能在警报素的生物合成中发挥作用，其作用模式不同于 RelA-SpoT 同源物。
Bacterial alarmone (p)ppGpp, is a global regulator responsible for the stringent control. Two homologous (p)ppGpp synthetases, RelA and SpoT, have been identified and characterized in Escherichia coli, whereas Gram-positive bacteria such as Bacillus subtilis have been thought to possess only a single RelA-SpoT enzyme. We have now identified two genes, yjbM and ywaC, in B. subtilis that encode a novel type of alarmone synthetase. The predicted products of these genes are relatively small proteins (similar to 25 kDa) that correspond to the (p)ppGpp synthetase domain of RelA-SpoT family members. A database survey revealed that genes homologous to yjbM and ywaC are conserved in certain bacteria belonging to Firmicutes or Actinobacteria phyla but not in other phyla such as Proteobacteria. We designated the proteins as small alarmone synthetases (SASs) to distinguish them from RelA-SpoT proteins. The (p)ppGpp synthetase function of YjbM and YwaC was confirmed by genetic complementation analysis and by in vitro assay of enzyme activity. Molecular genetic analysis also revealed that ywaC is induced by alkaline shock, resulting in the transient accumulation of ppGpp. The SAS proteins thus likely function in the biosynthesis of alarmone with a mode of action distinct from that of RelA-SpoT homologues.