Department of Biochemistry and Molecular Biology and Centre for Blood Research, The University of British Columbia, Vancouver V6T 1Z3 BC, Canada.
Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Richardson Road, Newcastle upon Tyne, NE2 4AX, UK.
Structure. 2020 Jun 2;28(6):643-650.e5. doi: 10.1016/j.str.2020.03.012. Epub 2020 Apr 21.
Peptidoglycan (PG) is an essential component of the bacterial cell wall and is assembled from a lipid II precursor by glycosyltransferase and transpeptidase reactions catalyzed in particular by bifunctional class A penicillin-binding proteins (aPBPs). In the major clinical pathogen Pseudomonas aeruginosa, PBP1B is anchored within the cytoplasmic membrane but regulated by a bespoke outer membrane-localized lipoprotein known as LpoP. Here, we report the structure of LpoP, showing an extended N-terminal, flexible tether followed by a well-ordered C-terminal tandem-tetratricopeptide repeat domain. We show that LpoP stimulates both PBP1B transpeptidase and glycosyltransferase activities in vitro and interacts directly via its C terminus globular domain with the central UB2H domain of PBP1B. Contrary to the situation in E. coli, P. aeruginosa CpoB does not regulate PBP1B/LpoP in vitro. We propose a mechanism that helps to underscore similarities and differences in class A PBP activation across Gram-negative bacteria.
肽聚糖 (PG) 是细菌细胞壁的重要组成部分，由脂质 II 前体通过糖基转移酶和转肽酶反应组装而成，这些反应特别由双功能 A 类青霉素结合蛋白 (aPBP) 催化。在主要的临床病原体铜绿假单胞菌中，PBP1B 锚定在内质膜中，但受一种独特的位于外膜上的脂蛋白 LpoP 调节。在这里，我们报告了 LpoP 的结构，显示了一个伸展的 N 端、柔性系绳，其后是一个有序的 C 端串联四肽重复结构域。我们表明 LpoP 在体外同时刺激 PBP1B 的转肽酶和糖基转移酶活性，并通过其 C 端球状结构域直接与 PBP1B 的中央 UB2H 结构域相互作用。与大肠杆菌的情况相反，铜绿假单胞菌 CpoB 不能在体外调节 PBP1B/LpoP。我们提出了一种机制，有助于强调革兰氏阴性菌中 A 类 PBP 激活的相似性和差异性。
