Department of Biological Sciences, Myongji University, Yongin, 17058, Republic of Korea.
J Microbiol. 2021 Jul;59(7):666-674. doi: 10.1007/s12275-021-1130-8. Epub 2021 May 15.
The inner membrane protein lipopolysaccharide assembly protein B (LapB) is an adaptor protein that activates the proteolysis of LpxC by an essential inner membrane metalloprotease, FtsH, leading to a decrease in the level of lipopolysaccharide in the membrane. In this study, we revealed the mechanism by which the essential inner membrane protein YejM regulates LapB and analyzed the role of the transmembrane domain of LapB in Escherichia coli. The transmembrane domain of YejM genetically and physically interacted with LapB and inhibited its function, which led to the accumulation of LpxC. The transmembrane domain of LapB was indispensable for both its physical interaction with YejM and its regulation of LpxC proteolysis. Notably, we found that the lapB mutant exhibited strong cold sensitivity and this phenotype was not associated with increased accumulation of LpxC. The transmembrane domain of LapB was also required for its role in adaptation to cold stress. Taken together, these results showed that LapB plays an important role in both the regulation of LpxC level, which is controlled by its interaction with the transmembrane domain of YejM, and adaptation to cold stress, which is independent of LpxC.
内膜蛋白脂多糖组装蛋白 B（LapB）是一种衔接蛋白，可激活必需内膜金属蛋白酶 FtsH 对 LpxC 的蛋白水解，导致膜中脂多糖水平降低。在这项研究中，我们揭示了必需内膜蛋白 YejM 调节 LapB 的机制，并分析了 LapB 跨膜结构域在大肠杆菌中的作用。YejM 的跨膜结构域在遗传和物理上与 LapB 相互作用并抑制其功能，导致 LpxC 积累。LapB 的跨膜结构域对于其与 YejM 的物理相互作用及其对 LpxC 蛋白水解的调节都是必不可少的。值得注意的是，我们发现 lapB 突变体表现出强烈的冷敏感性，这种表型与 LpxC 的积累增加无关。LapB 的跨膜结构域对于其适应冷应激的作用也是必需的。总之，这些结果表明 LapB 在调节 LpxC 水平方面发挥着重要作用，这种调节是通过其与 YejM 的跨膜结构域相互作用来控制的，并且在适应冷应激方面发挥着重要作用，这与 LpxC 无关。
