Department of Microbiology & Immunology, University of California, San Francisco, San Francisco, CA 94158, USA.
Cell. 2010 Dec 23;143(7):1097-109. doi: 10.1016/j.cell.2010.11.038.
Growth of the mesh-like peptidoglycan (PG) sacculus located between the bacterial inner and outer membranes (OM) is tightly regulated to ensure cellular integrity, maintain cell shape, and orchestrate division. Cytoskeletal elements direct placement and activity of PG synthases from inside the cell, but precise spatiotemporal control over this process is poorly understood. We demonstrate that PG synthases are also controlled from outside of the sacculus. Two OM lipoproteins, LpoA and LpoB, are essential for the function, respectively, of PBP1A and PBP1B, the major E. coli bifunctional PG synthases. Each Lpo protein binds specifically to its cognate PBP and stimulates its transpeptidase activity, thereby facilitating attachment of new PG to the sacculus. LpoB shows partial septal localization, and our data suggest that the LpoB-PBP1B complex contributes to OM constriction during cell division. LpoA/LpoB and their PBP-docking regions are restricted to γ-proteobacteria, providing models for niche-specific regulation of sacculus growth.
位于细菌内膜和外膜 (OM) 之间的网格状肽聚糖 (PG) 囊泡的生长受到严格调控，以确保细胞完整性、维持细胞形状并协调分裂。细胞骨架元素从细胞内部指导 PG 合成酶的放置和活性，但对这一过程的精确时空控制仍知之甚少。我们证明 PG 合成酶也受到囊泡外部的控制。两种 OM 脂蛋白，LpoA 和 LpoB，分别是主要的大肠杆菌双功能 PG 合成酶 PBP1A 和 PBP1B 的功能所必需的。每个 Lpo 蛋白都特异性地结合其同源 PBP 并刺激其转肽酶活性，从而促进新 PG 与囊泡的附着。LpoB 显示出部分隔膜定位，并且我们的数据表明 LpoB-PBP1B 复合物有助于细胞分裂期间 OM 的收缩。LpoA/LpoB 及其 PBP 对接区域仅限于γ-变形菌，为囊泡生长的特定小生境调节提供了模型。
