Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720.
Department of Molecular Cell Biology, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands.
Proc Natl Acad Sci U S A. 2019 May 28;116(22):10962-10967. doi: 10.1073/pnas.1905900116. Epub 2019 May 13.
Polar growth in 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.
极地生长在 海盗 并重新利用了众所周知的细菌细胞周期蛋白,如 FtsZ、FtsA、PopZ 和 PodJ。在这里,我们鉴定了一种以前未知的蛋白质,由于其在极地生长过程中作为生长极六聚体环的惊人定位,我们将其命名为生长极环(GPR)。GPR 还在细胞周期的中后期定位于细胞中部,就在分裂前,此时它准备在新的分裂子细胞中精确定位到新的生长极。GPR 长 2115 个氨基酸,具有两个 N 端跨膜结构域,将大部分蛋白质定位在细胞质中,N 端和 C 端富含脯氨酸的无序区域,以及一个包含 1700 个连续 α-螺旋结构域的大型中央区域。后一区域包含 12 个预测的相邻或重叠的载脂蛋白结构域,可能在极地生长过程中用于隔离脂质。稳定的遗传缺失或核糖体开关控制的耗竭导致球形细胞生长不良;因此,GPR 对于野生型生长和形态是必需的。由于 GPR 没有预测的酶结构域,并且它形成一个独特的 200nm 直径的环,我们提出 GPR 是肽聚糖和膜合成的组织中心的结构组成部分,对于细胞 envelope 在极地生长过程中的形成至关重要。GPR 同源物存在于许多 Rhizobiales 中;因此,我们的结果和提出的模型对于理解各种细菌物种的极地生长策略具有基础性意义。