Biology Department, Canisius College, Buffalo, New York, USA.
Department of BioSciences, Rice University, Houston, Texas, USA.
J Bacteriol. 2020 Dec 18;203(2). doi: 10.1128/JB.00463-20.
Previous work identified gene product 56 (gp56), encoded by the lytic bacteriophage SP01, as being responsible for inhibition of cell division during its infection. Assembly of the essential tubulin-like protein FtsZ into a ring-shaped structure at the nascent site of cytokinesis determines the timing and position of division in most bacteria. This FtsZ ring serves as a scaffold for recruitment of other proteins into a mature division-competent structure permitting membrane constriction and septal cell wall synthesis. Here, we show that expression of the predicted 9.3-kDa gp56 of SP01 inhibits later stages of cell division without altering FtsZ ring assembly. Green fluorescent protein-tagged gp56 localizes to the membrane at the site of division. While its localization does not interfere with recruitment of early division proteins, gp56 interferes with the recruitment of late division proteins, including Pbp2b and FtsW. Imaging of cells with specific division components deleted or depleted and two-hybrid analyses suggest that gp56 localization and activity depend on its interaction with FtsL. Together, these data support a model in which gp56 interacts with a central part of the division machinery to disrupt late recruitment of the division proteins involved in septal cell wall synthesis. Studies over the past decades have identified bacteriophage-encoded factors that interfere with host cell shape or cytokinesis during viral infection. The phage factors causing cell filamentation that have been investigated to date all act by targeting FtsZ, the conserved prokaryotic tubulin homolog that composes the cytokinetic ring in most bacteria and some groups of archaea. However, the mechanisms of several phage factors that inhibit cytokinesis, including gp56 of bacteriophage SP01 of , remain unexplored. Here, we show that, unlike other published examples of phage inhibition of cytokinesis, gp56 blocks cell division without targeting FtsZ. Rather, it utilizes the assembled FtsZ cytokinetic ring to localize to the division machinery and to block recruitment of proteins needed for septal cell wall synthesis.
先前的工作确定了裂解噬菌体 SP01 编码的产物 56（gp56）负责在感染过程中抑制细胞分裂。在大多数细菌中，将必需的微管样蛋白 FtsZ 组装成一个环形状结构，位于细胞分裂的新生位点，决定了分裂的时间和位置。这个 FtsZ 环作为招募其他蛋白质进入成熟的有分裂能力的结构的支架，允许膜收缩和隔膜细胞壁合成。在这里，我们表明，SP01 的预测 9.3 kDa gp56 的表达抑制了细胞分裂的后期阶段，而不改变 FtsZ 环的组装。绿色荧光蛋白标记的 gp56 定位于分裂部位的膜上。虽然它的定位不干扰早期分裂蛋白的招募，但 gp56 干扰了晚期分裂蛋白的招募，包括 Pbp2b 和 FtsW。对具有特定分裂成分缺失或耗尽的细胞进行成像和双杂交分析表明，gp56 的定位和活性依赖于其与 FtsL 的相互作用。总的来说，这些数据支持了一个模型，即 gp56 与分裂机制的中心部分相互作用，破坏涉及隔膜细胞壁合成的分裂蛋白的晚期招募。过去几十年的研究已经确定了噬菌体编码的因子，这些因子在病毒感染期间干扰宿主细胞的形状或细胞分裂。迄今为止，研究过的导致细胞丝状化的噬菌体因子都通过靶向 FtsZ 起作用，FtsZ 是一种保守的原核微管同源物，构成了大多数细菌和一些古菌群体的细胞分裂环。然而，包括噬菌体 SP01 的 gp56 在内的几种抑制细胞分裂的噬菌体因子的机制仍未被探索。在这里，我们表明，与其他已发表的噬菌体抑制细胞分裂的例子不同，gp56 不针对 FtsZ 就可以阻断细胞分裂。相反，它利用组装好的 FtsZ 细胞分裂环定位到分裂机制，并阻止隔膜细胞壁合成所需的蛋白质的招募。
