Peptidoglycan (PG) is a mesh-like heteropolymer made up of glycan chains cross-linked by short peptides and is the major scaffold of eubacterial cell walls, determining cell shape, size, and chaining. This structure, which is required for growth and survival, is located outside of the cytoplasmic membrane of bacterial cells, making it highly accessible to antibiotics. Penicillin-binding proteins (PBPs) are essential for construction of PG and perform transglycosylase activities to generate the glycan strands and transpeptidation to cross-link the appended peptides. The β-lactam antibiotics, which are among the most clinically effective antibiotics for the treatment of bacterial infections, inhibit PBP transpeptidation, ultimately leading to cell lysis. Despite this importance, the discrete functions of individual PBP homologues have been difficult to determine. These major gaps in understanding of PBP activation and macromolecular interactions largely result from a lack of tools to assess the functional state of specific PBPs in bacterial cells. We have identified β-lactones as a privileged scaffold for the generation of PBP-selective probes and utilized these compounds for imaging of the essential proteins, PBP2x and PBP2b, in Streptococcus pneumoniae. We demonstrated that while PBP2b activity is restricted to a ring surrounding the division sites, PBP2x activity is present both at the septal center and at the surrounding ring. These spatially separate regions of PBP2x activity could not be detected by previous activity-based approaches, which highlights a critical strength of our PBP-selective imaging strategy.

中文翻译：

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新型亲电子支架成像肺炎链球菌中的基本青霉素结合蛋白。

肽聚糖（PG）是一种网状的杂聚物，由短肽交联的聚糖链组成，是真细菌细胞壁的主要骨架，可决定细胞的形状，大小和链。生长和存活所必需的这种结构位于细菌细胞的细胞质膜之外，从而使抗生素高度易于使用。青霉素结合蛋白（PBP）对于PG的构建至关重要，并执行转糖基酶活性以生成聚糖链和进行转肽作用以使附加的肽交联。β-内酰胺抗生素是治疗细菌感染的临床上最有效的抗生素之一，可抑制PBP转肽作用，最终导致细胞溶解。尽管如此重要 单个PBP同源物的离散功能很难确定。这些对PBP活化和大分子相互作用的理解上的主要差距主要是由于缺乏评估细菌细胞中特定PBP功能状态的工具。我们已将β-内酯鉴定为生成PBP选择性探针的优先支架，并利用这些化合物对必需蛋白PBP2x和PBP2b进行了成像。肺炎链球菌。我们证明了，虽然PBP2b的活性仅限于分裂位点周围的环，但PBP2x的活性既存在于间隔中央，也存在于周围的环上。以前的基于活动的方法无法检测到PBP2x活动的这些空间上分开的区域，这突出了我们的PBP选择性成像策略的关键强度。