Although bacteria have diverse membrane proteins, the function of many of them remains unknown or uncertain even in Escherichia coli. In this study, to investigate the function of hypothetical membrane proteins, genome-wide analysis of phenotypes of hypothetical membrane proteins was performed under various envelope stresses. Several genes responsible for adaptation to envelope stresses were identified. Among them, deletion of YhcB, a conserved inner membrane protein of unknown function, caused high sensitivities to various envelope stresses and increased membrane permeability, and caused growth defect under normal growth conditions. Furthermore, yhcB deletion resulted in morphological aberration, such as branched shape, and cell division defects, such as filamentous growth and the generation of chromosome-less cells. The analysis of antibiotic susceptibility showed that the yhcB mutant was highly susceptible to various anti-folate antibiotics. Notably, all phenotypes of the yhcB mutant were completely or significantly restored by YhcB without the transmembrane domain, indicating that the localization of YhcB on the inner membrane is dispensable for its function. Taken together, our results demonstrate that YhcB is involved in cell morphology and cell division in a membrane localization-independent manner.

中文翻译：

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大肠杆菌中保守的内膜蛋白YhcB的表型表征。

尽管细菌具有多种膜蛋白，但即使在大肠杆菌中，许多细菌的功能仍然未知或不确定。在这项研究中，为了研究假设的膜蛋白的功能，在各种包膜压力下对假设的膜蛋白的表型进行全基因组分析。鉴定了几种负责适应包膜应力的基因。其中，YhcB（一种功能未知的保守内膜蛋白）的缺失引起了对各种包膜应力的高度敏感性，并增加了膜通透性，并在正常生长条件下引起了生长缺陷。此外，yhcB缺失导致形态畸变，例如分支形状，以及细胞分裂缺陷，例如丝状生长和无染色体细胞的产生。抗生素敏感性分析表明，yhcB突变株对各种抗叶酸抗生素高度敏感。值得注意的是，yhcB突变体的所有表型都被没有跨膜结构域的YhcB完全或显着还原，表明YhcB在内膜上的定位对其功能是必不可少的。两者合计，我们的结果表明，YhcB以膜定位独立的方式参与细胞形态和细胞分裂。