Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, 18011 Granada, Spain.
Departamento de Microbiología, Facultad de Ciencias, Universidad de Granada, Avda, Fuentenueva s/n, 18071 Granada, Spain.
Int J Mol Sci. 2022 Mar 25;23(7):3601. doi: 10.3390/ijms23073601.
Extracytoplasmic function (ECF) sigma factors are subunits of the RNA polymerase specialized in activating the transcription of a subset of genes responding to a specific environmental condition. The signal-transduction pathways where they participate can be activated by diverse mechanisms. The most common mechanism involves the action of a membrane-bound anti-sigma factor, which sequesters the ECF sigma factor, and releases it after the stimulus is sensed. However, despite most of these systems following this canonical regulation, there are many ECF sigma factors exhibiting a non-canonical regulatory mechanism. In this review, we aim to provide an updated and comprehensive view of the different activation mechanisms known for non-canonical ECF sigma factors, detailing their inclusion to the different phylogenetic groups and describing the mechanisms of regulation of some of their representative members such as EcfG from , showing a partner-switch mechanism; EcfP from , with a phosphorylation-dependent mechanism; or CorE from , regulated by a metal-sensing C-terminal extension.
细胞外功能（ECF）σ因子是 RNA 聚合酶的亚基，专门激活对特定环境条件做出反应的一组基因的转录。它们参与的信号转导途径可以通过多种机制激活。最常见的机制涉及膜结合反σ因子的作用，该反σ因子会隔离 ECF σ因子，并在感知到刺激后释放它。然而，尽管这些系统大多数遵循这种规范调节，但也有许多 ECF σ因子表现出非规范的调节机制。在这篇综述中，我们旨在提供一个关于非规范 ECF σ因子的不同激活机制的最新和全面的观点，详细描述它们在不同系统发育群中的包含情况，并描述它们的一些代表性成员的调节机制，例如来自 的 EcfG，具有伴侣转换机制；来自 的 EcfP，具有磷酸化依赖性机制；或来自 的 CorE，由金属感应 C 末端延伸调节。
