Department of Biology, Washington University, Saint Louis, Missouri, United States of America.
PLoS Genet. 2013;9(7):e1003663. doi: 10.1371/journal.pgen.1003663. Epub 2013 Jul 25.
Growth rate and nutrient availability are the primary determinants of size in single-celled organisms: rapidly growing Escherichia coli cells are more than twice as large as their slow growing counterparts. Here we report the identification of the glucosyltransferase OpgH as a nutrient-dependent regulator of E. coli cell size. During growth under nutrient-rich conditions, OpgH localizes to the nascent septal site, where it antagonizes assembly of the tubulin-like cell division protein FtsZ, delaying division and increasing cell size. Biochemical analysis is consistent with OpgH sequestering FtsZ from growing polymers. OpgH is functionally analogous to UgtP, a Bacillus subtilis glucosyltransferase that inhibits cell division in a growth rate-dependent fashion. In a striking example of convergent evolution, OpgH and UgtP share no homology, have distinct enzymatic activities, and appear to inhibit FtsZ assembly through different mechanisms. Comparative analysis of E. coli and B. subtilis reveals conserved aspects of growth rate regulation and cell size control that are likely to be broadly applicable. These include the conservation of uridine diphosphate glucose as a proxy for nutrient status and the use of moonlighting enzymes to couple growth rate-dependent phenomena to central metabolism.
在单细胞生物中，生长速度和营养可用性是决定大小的主要因素：快速生长的大肠杆菌细胞比缓慢生长的细胞大两倍多。在这里，我们报告了葡糖基转移酶 OpgH 作为一种营养依赖性的大肠杆菌细胞大小调节剂的鉴定。在营养丰富的条件下生长时，OpgH 定位于新生隔膜部位，在那里它拮抗微管样细胞分裂蛋白 FtsZ 的组装，延迟分裂并增加细胞大小。生化分析与 OpgH 将 FtsZ 从生长聚合物中隔离出来一致。OpgH 在功能上类似于枯草芽孢杆菌的葡糖基转移酶 UgtP，它以生长速度依赖的方式抑制细胞分裂。在趋同进化的一个显著例子中，OpgH 和 UgtP 没有同源性，具有不同的酶活性，并且似乎通过不同的机制抑制 FtsZ 组装。大肠杆菌和枯草芽孢杆菌的比较分析揭示了生长速度调节和细胞大小控制的保守方面，这些方面可能具有广泛的适用性。其中包括将尿苷二磷酸葡萄糖作为营养状况的替代物的保守性，以及利用兼职酶将生长速度依赖性现象与中心代谢联系起来。
