Dual function of LapB (YciM) in regulating Escherichia coli lipopolysaccharide synthesis

• 成果类型: Article
• 署名作者: Shu, Sheng; Tsutsui, Yuko; Nathawat, Rajkanwar; Mi, Wei
• 署名单位: Yale University; Yale University; Yale University
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-12373
• DOI: 10.1073/pnas.2321510121
• 发表日期: 2024-04-23
• 关键词: ftsh protein; lpxc; deacetylase; biosynthesis; degradation; gene; rubredoxin; substrate; enzyme; step

摘要

Levels of lipopolysaccharide (LPS), an essential glycolipid on the surface of most gramnegative bacteria, are tightly controlled-making LPS synthesis a promising target for developing new antibiotics. Escherichia coli adaptor protein LapB (YciM) plays an important role in regulating LPS synthesis by promoting degradation of LpxC, a deacetylase that catalyzes the first committed step in LPS synthesis. Under conditions where LPS is abundant, LapB recruits LpxC to the AAA+ protease FtsH for degradation. LapB achieves this by simultaneously interacting with FtsH through its transmembrane helix and LpxC through its cytoplasmic domain. Here, we describe a cryo - EM structure of the complex formed between LpxC and the cytoplasmic domain of LapB (Lap B cyto ). The structure reveals how LapB exploits both its tetratricopeptide repeat (TPR) motifs and rubredoxin domain to interact with LpxC. Through both in vitro and in vivo analysis, we show that mutations at the LapB cyto /LpxC interface prevent LpxC degradation. Unexpectedly, binding to LapB cyto also inhibits the enzymatic activity of LpxC through allosteric effects reminiscent of LpxC activation by MurA in Pseudomonas aeruginosa. Our findings argue that LapB regulates LPS synthesis in two steps: In the first step, LapB inhibits the activity of LpxC, and in the second step, it commits LpxC to degradation by FtsH.