Pushing the Envelope: The Mysterious Journey Through the Bacterial Secretory Machinery, and Beyond.
Pushing the Envelope: The Mysterious Journey Through the Bacterial Secretory Machinery, and Beyond.
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DOI：
10.3389/fmicb.2021.782900
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发表时间：
2021
影响因子：
5.2
通讯作者：
Collinson I
中科院分区：
文献类型：
--
作者：
Troman LA;Collinson I
革兰氏阴性菌被包含在由内外膜组成的包膜中，内外膜之间有肽聚糖（PG）层。蛋白质转运穿过内膜进行分泌或插入内膜主要使用高度保守的沙漏形通道SecYEG进行：Sec易位子的核心复合物。该转运过程通过与辅助亚复合物SecDF-YajC（分泌）和YidC（插入）的相互作用来促进，形成全-转位子（HTL）。本文综述了跨内膜的转运过程，并进一步探讨了如何实现递送和折叠到周质或外膜。蛋白质被丢弃到周质中，任其自生自灭，这似乎是不可能的。事实上，已知分子伴侣如SurA、Skp、DegP在蛋白质折叠、质量控制以及必要时的降解中起作用。YfgM和PpiD，通过它们在Sec机器的周质表面的结合，最有可能也以某种方式参与。然而，目前还不完全清楚外膜蛋白是如何通过蛋白酶和PG走私到桶装配机械（BAM）和它们的最终目的地。此外，如何才能做到这一点，因为人们认为，没有能源的投入？最近，我们提出，SEC和BAM translocons相互作用，最有可能的其他因素，提供一个管道的周质和外膜。碰巧的是，许多其他专门的蛋白质分泌系统也为此目的形成了跨包膜结构。跨膜组分间的直接相互作用提高了从内膜到外膜主动转运的能量耦合的前景。实际上，这种通过大的膜间组件的长程能量耦合发生在小分子输入（例如，通过Ton复合体的营养物输入）和输出（例如，AcrAB-TolC复合物的药物外排）。本文将考虑这一假设的前景的背景下，外膜蛋白的生物合成。
Gram-negative bacteria are contained by an envelope composed of inner and outer-membranes with the peptidoglycan (PG) layer between them. Protein translocation across the inner membrane for secretion, or insertion into the inner membrane is primarily conducted using the highly conserved, hourglass-shaped channel, SecYEG: the core-complex of the Sec translocon. This transport process is facilitated by interactions with ancillary subcomplex SecDF-YajC (secretion) and YidC (insertion) forming the holo-translocon (HTL). This review recaps the transport process across the inner-membrane and then further explores how delivery and folding into the periplasm or outer-membrane is achieved. It seems very unlikely that proteins are jettisoned into the periplasm and left to their own devices. Indeed, chaperones such as SurA, Skp, DegP are known to play a part in protein folding, quality control and, if necessary degradation. YfgM and PpiD, by their association at the periplasmic surface of the Sec machinery, most probably are also involved in some way. Yet, it is not entirely clear how outer-membrane proteins are smuggled past the proteases and across the PG to the barrel-assembly machinery (BAM) and their final destination. Moreover, how can this be achieved, as is thought, without the input of energy? Recently, we proposed that the Sec and BAM translocons interact with one another, and most likely other factors, to provide a conduit to the periplasm and the outer-membrane. As it happens, numerous other specialized proteins secretion systems also form trans-envelope structures for this very purpose. The direct interaction between components across the envelope raises the prospect of energy coupling from the inner membrane for active transport to the outer-membrane. Indeed, this kind of long-range energy coupling through large inter-membrane assemblies occurs for small molecule import (e.g., nutrient import by the Ton complex) and export (e.g., drug efflux by the AcrAB-TolC complex). This review will consider this hypothetical prospect in the context of outer-membrane protein biogenesis.
周质伴侣 Skp 对外膜蛋白摄取的直接观察
影响因子：
3.7
作者：
Lyu ZX;Shao Q;Gao YQ;Zhao XS
通讯作者：
Zhao XS