GROWTH POLE RING protein forms a 200-nm-diameter ring structure essential for polar growth and rod shape in Agrobacterium tumefaciens
GROWTH POLE RING protein forms a 200-nm-diameter ring structure essential for polar growth and rod shape in Agrobacterium tumefaciens
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DOI：
10.1073/pnas.1905900116
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发表时间：
2019-05
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通讯作者：
John R. Zupan;Romain Grangeon;J. S. Robalino-Espinosa;J. S. Robalino-Espinosa;N. Garnica;Patricia Zambryski-Patricia
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作者：
John R. Zupan;Romain Grangeon;J. S. Robalino-Espinosa;J. S. Robalino-Espinosa;N. Garnica;Patricia Zambryski-Patricia
意义广泛研究的杆状细菌大肠杆菌、枯草芽孢杆菌和新月柄杆菌通过新的细胞壁物质沿着整个细胞长度分散插入而生长。一些放射菌目和变形菌门使用另一种原核生长模式--极性生长。后一门包括根瘤菌科，其中根癌农杆菌是一个突出的成员。导致极性增长的因素在很大程度上是未知的。在这里，我们描述了生长极环（GPR）蛋白从农杆菌与一个惊人的定位为一个环的六个焦点在生长极。GPR可能是农杆菌中的极性生长组织者，因为它的缺失导致严重的形态缺陷，包括圆柱形细胞形状的丧失，而它的过量产生导致异位生长极。农杆菌中的极性生长海盗和重新利用众所周知的细菌细胞周期蛋白，如FtsZ，FtsA，PopZ和PodJ。在这里，我们确定了一个迄今未知的蛋白质，我们命名为生长极环（GPR），由于其惊人的本地化作为一个六聚体环在极性生长过程中的生长极。GPR还定位于细胞周期后期的中细胞，就在分裂之前，然后它准备精确地定位于兄弟细胞中的新生长极。GPR长2，115 aa，具有两个N-末端跨膜结构域，将蛋白质的大部分置于细胞质中，N-和C-末端富含脯氨酸的无序区域，以及连续α-螺旋结构域的大的1，700-aa中心区域。后一个区域包含12个预测的相邻或重叠的载脂蛋白结构域，其可能在极性生长期间起隔离脂质的作用。稳定的基因缺失或核糖开关控制的耗竭导致球形细胞生长不良;因此，GPR对野生型生长和形态至关重要。由于GPR没有预测的酶结构域，它形成了一个独特的200 nm直径的环，我们建议，GPR是一个组织中心的肽聚糖和膜合成的关键细胞包膜形成在极性生长的结构组成部分。GPR同源物在许多根瘤菌目中被发现，因此，我们的研究结果和提出的模型是了解极性生长策略在各种细菌物种的基础。
Significance The extensively studied rod-shaped bacteria Escherichia coli, Bacillus subtilis, and Caulobacter crescentus grow by dispersed insertion of new cell wall material along the entire length of the cell. An alternative prokaryotic growth mode—polar growth—is used by some Actinomycetales and Proteobacteria. The latter phylum includes the family Rhizobiaceae, of which Agrobacterium tumefaciens is a prominent member. The factors responsible for polar growth are largely unknown. Here we describe GROWTH POLE RING (GPR) protein from Agrobacterium with a striking localization as a ring of six foci at the growth pole. GPR is potentially the polar growth organizer in Agrobacterium, as its absence leads to severe morphological defects, including loss of cylindrical cell shape, while its overproduction leads to ectopic growth poles. Polar growth in Agrobacterium pirates and repurposes well-known bacterial cell cycle proteins, such as FtsZ, FtsA, PopZ, and PodJ. Here we identify a heretofore unknown protein that we name GROWTH POLE RING (GPR) due to its striking localization as a hexameric ring at the growth pole during polar growth. GPR also localizes at the midcell late in the cell cycle just before division, where it is then poised to be precisely localized at new growth poles in sibling cells. GPR is 2,115 aa long, with two N-terminal transmembrane domains placing the bulk of the protein in the cytoplasm, N- and C-terminal proline-rich disordered regions, and a large 1,700-aa central region of continuous α-helical domains. This latter region contains 12 predicted adjacent or overlapping apolipoprotein domains that may function to sequester lipids during polar growth. Stable genetic deletion or riboswitch-controlled depletion results in spherical cells that grow poorly; thus, GPR is essential for wild-type growth and morphology. As GPR has no predicted enzymatic domains and it forms a distinct 200-nm-diameter ring, we propose that GPR is a structural component of an organizing center for peptidoglycan and membrane syntheses critical for cell envelope formation during polar growth. GPR homologs are found in numerous Rhizobiales; thus, our results and proposed model are fundamental to understanding polar growth strategy in a variety of bacterial species.