Department of Microbiology and Immunobiology, Harvard Medical School; Boston, MA 02115;
The Florey Institute, University of Sheffield, S10 2TN Sheffield, United Kingdom.
Proc Natl Acad Sci U S A. 2018 Mar 13;115(11):2812-2817. doi: 10.1073/pnas.1715218115. Epub 2018 Feb 27.
Most bacterial cells are surrounded by an essential cell wall composed of the net-like heteropolymer peptidoglycan (PG). Growth and division of bacteria are intimately linked to the expansion of the PG meshwork and the construction of a cell wall septum that separates the nascent daughter cells. Class A penicillin-binding proteins (aPBPs) are a major family of PG synthases that build the wall matrix. Given their central role in cell wall assembly and importance as drug targets, surprisingly little is known about how the activity of aPBPs is controlled to properly coordinate cell growth and division. Here, we report the identification of MacP (SPD_0876) as a membrane-anchored cofactor of PBP2a, an aPBP synthase of the Gram-positive pathogen We show that MacP localizes to the division site of , forms a complex with PBP2a, and is required for the in vivo activity of the synthase. Importantly, MacP was also found to be a substrate for the kinase StkP, a global cell cycle regulator. Although StkP has been implicated in controlling the balance between the elongation and septation modes of cell wall synthesis, none of its substrates are known to modulate PG synthetic activity. Here we show that a phosphoablative substitution in MacP that blocks StkP-mediated phosphorylation prevents PBP2a activity without affecting the MacP-PBP2a interaction. Our results thus reveal a direct connection between PG synthase function and the control of cell morphogenesis by the StkP regulatory network.
大多数细菌细胞都被一层重要的细胞壁所包围,该细胞壁由网状的杂多糖肽聚糖(PG)组成。细菌的生长和分裂与 PG 网格的扩展以及分隔新生子细胞的细胞壁隔膜的构建密切相关。A 类青霉素结合蛋白(aPBPs)是合成细胞壁的 PG 合成酶的主要家族。鉴于它们在细胞壁组装中的核心作用以及作为药物靶点的重要性,人们对 aPBPs 的活性如何受到控制以正确协调细胞生长和分裂知之甚少。在这里,我们报告了 MacP(SPD_0876)作为革兰氏阳性病原体 的 PBP2a 的膜锚定辅因子的鉴定。我们表明 MacP 定位于 的分裂部位,与 PBP2a 形成复合物,并且是合成酶体内活性所必需的。重要的是,还发现 MacP 是激酶 StkP 的底物,StkP 是一种全局细胞周期调节剂。尽管 StkP 已被牵连控制细胞壁合成的伸长和分隔模式之间的平衡,但它的底物中没有一种已知可以调节 PG 合成活性。在这里,我们表明 MacP 中的一个阻止 StkP 介导的磷酸化的磷酸化缺失取代阻止了 PBP2a 的活性,而不影响 MacP-PBP2a 相互作用。因此,我们的结果揭示了 PG 合成酶功能与 StkP 调节网络控制细胞形态发生之间的直接联系。