Thomanek Nikolas, Arends Jan, Lindemann Claudia, Barkovits Katalin, Meyer Helmut E, Marcus Katrin, Narberhaus Franz
Medical Proteome Center, Ruhr University Bochum, Bochum, Germany.
Microbial Biology, Ruhr University Bochum, Bochum, Germany.
Front Microbiol. 2019 Jan 14;9:3285. doi: 10.3389/fmicb.2018.03285. eCollection 2018.
Lipopolysaccharides (LPS) in the outer membrane of Gram-negative bacteria provide the first line of defense against antibiotics and other harmful compounds. LPS biosynthesis critically depends on LpxC catalyzing the first committed enzyme in this process. In , the cellular concentration of LpxC is adjusted in a growth rate-dependent manner by the FtsH protease making sure that LPS biosynthesis is coordinated with the cellular demand. As a result, LpxC is stable in fast-growing cells and prone to degradation in slow-growing cells. One of the factors involved in this process is the alarmone guanosine tetraphosphate (ppGpp) but previous studies suggested the involvement of yet unknown factors in LpxC degradation. We established a quantitative proteomics approach aiming at the identification of proteins that are associated with LpxC and/or FtsH at high or low growth rates. The identification of known LpxC and FtsH interactors validated our approach. A number of proteins involved in fatty acid biosynthesis and degradation, including the central regulator FadR, were found in the LpxC and/or FtsH interactomes. Another protein associated with LpxC and FtsH was WaaH, a LPS-modifying enzyme. When overproduced, several members of the LpxC/FtsH interactomes were able to modulate LpxC proteolysis. Our results go beyond the previously established link between LPS and phospholipid biosynthesis and uncover a far-reaching network that controls LPS production by involving multiple enzymes in fatty acid metabolism, phospholipid biosynthesis and LPS modification.
革兰氏阴性菌外膜中的脂多糖（LPS）构成了抵御抗生素和其他有害化合物的第一道防线。LPS的生物合成关键依赖于LpxC，它催化该过程中的首个关键酶。在[具体内容缺失]中，FtsH蛋白酶以生长速率依赖的方式调节LpxC的细胞浓度，确保LPS生物合成与细胞需求相协调。因此，LpxC在快速生长的细胞中稳定，而在缓慢生长的细胞中易于降解。参与这一过程的因素之一是警报素四磷酸鸟苷（ppGpp），但先前的研究表明，LpxC降解还涉及其他未知因素。我们建立了一种定量蛋白质组学方法，旨在鉴定在高生长速率或低生长速率下与LpxC和/或FtsH相关的蛋白质。已知的LpxC和FtsH相互作用蛋白的鉴定验证了我们的方法。在LpxC和/或FtsH相互作用组中发现了许多参与脂肪酸生物合成和降解的蛋白质，包括核心调节因子FadR。另一种与LpxC和FtsH相关的蛋白质是WaaH，一种LPS修饰酶。当过量表达时，LpxC/FtsH相互作用组的几个成员能够调节LpxC的蛋白水解。我们的研究结果超越了先前建立的LPS与磷脂生物合成之间的联系，揭示了一个广泛的网络，该网络通过涉及脂肪酸代谢、磷脂生物合成和LPS修饰中的多种酶来控制LPS的产生。
