Dear editor, I am submitting this paper entitled “Genetic analysis of the septal peptidoglycan synthase FtsWI complex indicates a conserved activation mechanism for SEDS-bPBP complexes” as a research article in PLoS Genetics. SEDS family peptidoglycan (PG) glycosyltransferases RodA and FtsW require their cognate transpeptidases PBP2 and FtsI (class B penicillin binding proteins) to synthesize PG along the cell cylinder and at the septum, respectively. The activities of these SEDS-bPBPs complexes are tightly regulated to ensure proper cell elongation and division. In Escherichia coli FtsN switches FtsA and FtsQLB to the active forms that synergize to stimulate FtsWI, but the exact mechanism is not well understood. Previously, we isolated an activation mutation in ftsW (M269I) that allows cell division with reduced FtsN function. To try and understand the basis for activation we isolated additional substitutions at this position and found that only the original substitution produced an active mutant whereas drastic changes resulted in an inactive mutant. In another approach we isolated suppressors of an inactive FtsL mutant and obtained FtsW E289G and FtsI K211I and found they bypassed FtsN. Epistatic analysis of these mutations and others confirmed that the FtsN-triggered activation signal goes from FtsQLB to FtsI to FtsW. Mapping these mutations and others affecting the activities of FtsWI on the RodA-PBP2 structure revealed they are located at the interaction interface between the extracellular loop 4 (ECL4) of FtsW and the pedestal domain of FtsI (PBP3). This supports a model in which the interaction between the ECL4 of SEDS proteins and the pedestal domain of their cognate bPBPs plays a critical role in the activation mechanism.

中文翻译：

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间隔肽聚糖合酶FtsWI复合物的遗传分析支持SEDS-bPBP复合物的保守激活机制

亲爱的编辑，我作为PLoS Genetics上的一篇研究论文，提交了题为“间隔肽聚糖聚糖合酶FtsWI复合物的基因分析表明SEDS-bPBP复合物的保守激活机制”的论文。SEDS家族的肽聚糖（PG）糖基转移酶RodA和FtsW需要它们的同源转肽酶PBP2和FtsI（B类青霉素结合蛋白）才能沿细胞圆柱和隔垫分别合成PG。这些SEDS-bPBPs复合物的活性受到严格调节，以确保适当的细胞延长和分裂。在大肠杆菌中，FtsN将FtsA和FtsQLB转换为协同作用来刺激FtsWI的活性形式，但确切的机理尚不完全清楚。以前，我们在ftsW（M269I）中分离了一个激活突变，该突变允许FtsN功能降低的细胞分裂。为了尝试理解激活的基础，我们在该位置分离了其他取代基，发现只有原始取代基才产生活性突变体，而剧烈的变化则导致了无效突变体。在另一种方法中，我们分离了无活性的FtsL突变体的抑制子，获得了FtsW E289G和FtsI K211I，发现它们绕过了FtsN。对这些突变和其他突变的上位性分析证实，FtsN触发的激活信号从FtsQLB到FtsI再到FtsW。绘制这些突变以及其他影响FtsWI在RodA-PBP2结构上的活性的突变，发现它们位于FtsW的胞外环4（ECL4）和FtsI的基座域（PBP3）之间的相互作用界面上。