Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts, USA.
PLoS Pathog. 2010 Jul 29;6(7):e1001020. doi: 10.1371/journal.ppat.1001020.
Bacterial cell growth and division require coordinated cell wall hydrolysis and synthesis, allowing for the removal and expansion of cell wall material. Without proper coordination, unchecked hydrolysis can result in cell lysis. How these opposing activities are simultaneously regulated is poorly understood. In Mycobacterium tuberculosis, the resuscitation-promoting factor B (RpfB), a lytic transglycosylase, interacts and synergizes with Rpf-interacting protein A (RipA), an endopeptidase, to hydrolyze peptidoglycan. However, it remains unclear what governs this synergy and how it is coordinated with cell wall synthesis. Here we identify the bifunctional peptidoglycan-synthesizing enzyme, penicillin binding protein 1 (PBP1), as a RipA-interacting protein. PBP1, like RipA, localizes both at the poles and septa of dividing cells. Depletion of the ponA1 gene, encoding PBP1 in M. smegmatis, results in a severe growth defect and abnormally shaped cells, indicating that PBP1 is necessary for viability and cell wall stability. Finally, PBP1 inhibits the synergistic hydrolysis of peptidoglycan by the RipA-RpfB complex in vitro. These data reveal a post-translational mechanism for regulating cell wall hydrolysis and synthesis through protein-protein interactions between enzymes with antagonistic functions.
细菌细胞的生长和分裂需要协调的细胞壁水解和合成，以允许去除和扩展细胞壁材料。如果没有适当的协调，不受控制的水解可能导致细胞裂解。这些相反的活动是如何同时被调节的，目前还知之甚少。在结核分枝杆菌中，促复苏因子 B（RpfB），一种溶菌糖苷酶，与内切肽酶 Rpf 相互作用蛋白 A（RipA）相互作用并协同作用，以水解肽聚糖。然而，目前尚不清楚是什么控制了这种协同作用，以及它如何与细胞壁合成相协调。在这里，我们确定了具有双重功能的肽聚糖合成酶青霉素结合蛋白 1（PBP1），是 RipA 的相互作用蛋白。PBP1 与 RipA 一样，定位于分裂细胞的两极和隔膜处。分枝杆菌 smegmatis 中编码 PBP1 的 ponA1 基因缺失会导致严重的生长缺陷和形状异常的细胞，表明 PBP1 对于细胞活力和细胞壁稳定性是必需的。最后，PBP1 抑制 RipA-RpfB 复合物在体外协同水解肽聚糖。这些数据揭示了一种通过具有拮抗功能的酶之间的蛋白质-蛋白质相互作用来调节细胞壁水解和合成的翻译后机制。
