Department of Biochemistry, Duke University Medical Center, Durham, North Carolina, USA.
Center for Theragnosis, Biomedical Research Institute, Korea Institute of Science and Technology, Seoul, Republic of Korea.
mBio. 2019 Jun 18;10(3):e00886-19. doi: 10.1128/mBio.00886-19.
Although distinct lipid phosphatases are thought to be required for processing lipid A (component of the outer leaflet of the outer membrane), glycerophospholipid (component of the inner membrane and the inner leaflet of the outer membrane), and undecaprenyl pyrophosphate (C-PP; precursors of peptidoglycan and O antigens of lipopolysaccharide) in Gram-negative bacteria, we report that the lipid A 1-phosphatases, LpxEs, functionally connect multiple layers of cell envelope biogenesis in Gram-negative bacteria. We found that LpxE structurally resembles YodM in , a phosphatase for phosphatidylglycerol phosphate (PGP) with a weak activity on C-PP, and rescues deficient in PGP and C-PP phosphatase activities; deletion of in reduces the MIC value of bacitracin, indicating a significant contribution of LpxE to the native bacterial C-PP phosphatase activity. Suppression of plasmid-borne in deficient in chromosomally encoded C-PP phosphatase activities results in cell enlargement, loss of O-antigen repeats of lipopolysaccharide, and ultimately cell death. These discoveries implicate LpxE as the first example of a multifunctional regulatory enzyme that orchestrates lipid A modification, O-antigen production, and peptidoglycan biogenesis to remodel multiple layers of the Gram-negative bacterial envelope. Dephosphorylation of the lipid A 1-phosphate by LpxE in Gram-negative bacteria plays important roles in antibiotic resistance, bacterial virulence, and modulation of the host immune system. Our results demonstrate that in addition to removing the 1-phosphate from lipid A, LpxEs also dephosphorylate undecaprenyl pyrophosphate, an important metabolite for the synthesis of the essential envelope components, peptidoglycan and O-antigen. Therefore, LpxEs participate in multiple layers of biogenesis of the Gram-negative bacterial envelope and increase antibiotic resistance. This discovery marks an important step toward understanding the regulation and biogenesis of the Gram-negative bacterial envelope.
尽管人们认为在革兰氏阴性菌中，不同的脂质磷酸酶负责加工脂质 A（外膜的外层）、甘油磷脂（内膜和外膜的内层）和十一烯基焦磷酸（C-PP；肽聚糖和脂多糖 O 抗原的前体），但我们报告称，脂质 A 1-磷酸酶 LpxE 在革兰氏阴性菌中在多个层面的细胞包膜生物发生中具有功能联系。我们发现 LpxE 在结构上类似于来自的 YodM，YodM 是一种对磷酸甘油磷酸（PGP）具有弱活性的磷酸酶，对 C-PP 具有活性，并且可以拯救缺乏 PGP 和 C-PP 磷酸酶活性的突变体；在缺失的突变体中缺失会降低 bacitracin 的 MIC 值，表明 LpxE 对天然细菌 C-PP 磷酸酶活性有重要贡献。在缺失染色体编码的 C-PP 磷酸酶活性的突变体中抑制质粒携带的会导致细胞增大、丧失脂多糖的 O-抗原重复序列，最终导致细胞死亡。这些发现表明 LpxE 是第一个多功能调节酶的例子，它协调脂质 A 修饰、O-抗原产生和肽聚糖生物发生，以重塑革兰氏阴性细菌包膜的多个层面。LpxE 在革兰氏阴性菌中对脂质 A 1-磷酸的去磷酸化在抗生素耐药性、细菌毒力和宿主免疫系统调节中起着重要作用。我们的结果表明，除了从脂质 A 上去除 1-磷酸外，LpxE 还去磷酸化十一烯基焦磷酸，十一烯基焦磷酸是合成必需包膜成分肽聚糖和 O-抗原的重要代谢物。因此，LpxE 参与革兰氏阴性菌包膜的多个层面的生物发生，并增加抗生素耐药性。这一发现标志着朝着理解革兰氏阴性菌包膜的调节和生物发生迈出了重要一步。
