Woldemeskel Selamawit Abi, McQuillen Ryan, Hessel Alex M, Xiao Jie, Goley Erin D
Departments of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Mol Microbiol. 2017 Sep;105(5):721-740. doi: 10.1111/mmi.13731. Epub 2017 Jul 3.
The cytoskeletal GTPase FtsZ assembles at midcell, recruits the division machinery and directs envelope invagination for bacterial cytokinesis. ZapA, a conserved FtsZ-binding protein, promotes Z-ring stability and efficient division through a mechanism that is not fully understood. Here, we investigated the function of ZapA in Caulobacter crescentus. We found that ZapA is encoded in an operon with a small coiled-coil protein we named ZauP. ZapA and ZauP co-localized at the division site and were each required for efficient division. ZapA interacted directly with both FtsZ and ZauP. Neither ZapA nor ZauP influenced FtsZ dynamics or bundling, in vitro, however. Z-rings were diffuse in cells lacking zapA or zauP and, conversely, FtsZ was enriched at midcell in cells overproducing ZapA and ZauP. Additionally, FtsZ persisted at the poles longer when ZapA and ZauP were overproduced, and frequently colocalized with MipZ, a negative regulator of FtsZ polymerization. We propose that ZapA and ZauP promote efficient cytokinesis by stabilizing the midcell Z-ring through a bundling-independent mechanism. The zauPzapA operon is present in diverse Gram-negative bacteria, indicating a common mechanism for Z-ring assembly.
细胞骨架GTP酶FtsZ在细胞中部组装，募集分裂机制并引导包膜内陷以进行细菌胞质分裂。ZapA是一种保守的FtsZ结合蛋白，通过一种尚未完全了解的机制促进Z环的稳定性和高效分裂。在这里，我们研究了ZapA在新月柄杆菌中的功能。我们发现ZapA在一个操纵子中编码，该操纵子中有一个我们命名为ZauP的小卷曲螺旋蛋白。ZapA和ZauP在分裂位点共定位，并且都是高效分裂所必需的。ZapA直接与FtsZ和ZauP相互作用。然而，在体外，ZapA和ZauP都不影响FtsZ的动态变化或成束。在缺乏zapA或zauP的细胞中，Z环是弥散的，相反，在过量产生ZapA和ZauP的细胞中，FtsZ在细胞中部富集。此外，当过量产生ZapA和ZauP时，FtsZ在两极持续的时间更长，并且经常与FtsZ聚合的负调节因子MipZ共定位。我们提出，ZapA和ZauP通过一种不依赖于成束的机制稳定细胞中部的Z环，从而促进高效的胞质分裂。zauPzapA操纵子存在于多种革兰氏阴性细菌中，表明Z环组装存在一种共同机制。
