Department of Molecular Biology and Microbiology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, USA.
Department of Molecular Biology and Microbiology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, USA
J Bacteriol. 2019 Mar 26;201(8). doi: 10.1128/JB.00698-18. Print 2019 Apr 15.
Two key tasks of the bacterial septal-ring (SR) machinery during cell constriction are the generation of an inward-growing annulus of septal peptidoglycan (sPG) and the concomitant splitting of its outer edge into two layers of polar PG that will be inherited by the two new cell ends. FtsN is an essential SR protein that helps trigger the active constriction phase in by inducing a self-enhancing cycle of processes that includes both sPG synthesis and splitting and that we refer to as the sPG loop. DedD is an SR protein that resembles FtsN in several ways. Both are bitopic inner membrane proteins with small N-terminal cytoplasmic parts and larger periplasmic parts that terminate with a SPOR domain. Though absence of DedD normally causes a mild cell-chaining phenotype, the protein is essential for division and survival of cells with limited FtsN activity. Here, we find that a small N-terminal portion of DedD (DedD; DedD) is required and sufficient to suppress Δ-associated division phenotypes, and we identify residues within its transmembrane domain that are particularly critical to DedD function. Further analyses indicate that DedD and FtsN act in parallel to promote sPG synthesis, possibly by engaging different parts of the FtsBLQ subcomplex to induce a conformation that permits and/or stimulates the activity of sPG synthase complexes composed of FtsW, FtsI (PBP3), and associated proteins. We propose that, like FtsN, DedD promotes cell fission by stimulating sPG synthesis, as well as by providing positive feedback to the sPG loop. Cell division (cytokinesis) is a fundamental biological process that is incompletely understood for any organism. Division of bacterial cells relies on a ring-like machinery called the septal ring or divisome that assembles along the circumference of the mother cell at the site where constriction eventually occurs. In the well-studied bacterium , this machinery contains over 30 distinct proteins. We identify functionally important parts of one of these proteins, DedD, and present evidence supporting a role for DedD in helping to induce and/or sustain a self-enhancing cycle of processes that are executed by fellow septal-ring proteins and that drive the active constriction phase of the cell division cycle.
两个关键任务的细菌隔膜环（SR）机械在细胞收缩期间是生成向内生长的隔膜肽聚糖（sPG）的环和同时分裂的外边缘分成两层极地 PG，将继承两个新的细胞结束。FtsN 是一个必不可少的 SR 蛋白，有助于触发活跃的收缩阶段的 通过诱导一个自我增强的过程，包括 sPG 合成和分裂，我们称之为 sPG 循环。DedD 是一种类似于 FtsN 的 SR 蛋白。两者都是双位内膜蛋白，具有较小的 N 端细胞质部分和较大的周质部分，其末端带有 SPOR 结构域。虽然 DedD 的缺失通常会导致轻微的细胞连锁表型，但该蛋白对于具有有限 FtsN 活性的细胞的分裂和存活是必不可少的。在这里，我们发现 DedD 的一小部分 N 端（DedD）是必需的和足以抑制相关的分裂表型，并确定其跨膜结构域内的残基，这对 DedD 功能特别关键。进一步的分析表明，DedD 和 FtsN 平行作用以促进 sPG 合成，可能通过参与 FtsBLQ 亚复合物的不同部分来诱导允许和/或刺激由 FtsW、FtsI（PBP3）和相关蛋白组成的 sPG 合酶复合物的构象。我们提出，像 FtsN 一样，DedD 通过刺激 sPG 合成以及对 sPG 循环提供正反馈来促进细胞分裂。细胞分裂（有丝分裂）是一个基本的生物学过程，对于任何生物体来说都不完全了解。细菌细胞的分裂依赖于一种称为隔膜环或分裂体的环状机械装置，该装置在母细胞的圆周上组装，在最终发生收缩的部位。在研究得很好的 中，这种机械装置包含 30 多种不同的蛋白质。我们确定了其中一种蛋白质 DedD 的功能重要部分，并提供了支持 DedD 在帮助诱导和/或维持由其他隔膜环蛋白执行的自我增强过程的循环的证据，这些过程驱动了细胞分裂周期的活跃收缩阶段。
