Buss Jackson A, Peters Nick T, Xiao Jie, Bernhardt Thomas G
Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, 02115, USA.
Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, MD, 21205, USA.
Mol Microbiol. 2017 May;104(4):652-663. doi: 10.1111/mmi.13655. Epub 2017 Mar 26.
Cell division in Escherichia coli begins with the polymerization of FtsZ into a ring-like structure, the Z-ring, at midcell. All other division proteins are thought to require the Z-ring for recruitment to the future division site. Here, it is reported that the Z-ring associated proteins ZapA and ZapB form FtsZ-independent structures at midcell. Upon Z-ring disruption by the FtsZ polymerization antagonist SulA, ZapA remained at midcell as a cloud-like accumulation. Using ZapA(N60Y), a variant defective for interaction with FtsZ, it was established that these ZapA structures form without a connection to the Z-ring. Furthermore, midcell accumulations of GFP-ZapA(N60Y) often preceded Z-rings at midcell and required ZapB to assemble, suggesting that ZapB polymers form the foundation of these structures. In the absence of MatP, a DNA-binding protein that links ZapB to the chromosomal terminus region, cloud-like ZapA structures still formed but failed to track with the chromosome terminus and did not consistently precede FtsZ at midcell. Taken together, the results suggest that FtsZ-independent structures of ZapA-ZapB provide additional positional cues for Z-ring formation and may help coordinate its assembly with chromosome replication and segregation.
大肠杆菌中的细胞分裂始于FtsZ在细胞中部聚合成环状结构，即Z环。所有其他分裂蛋白都被认为需要Z环才能被招募到未来的分裂位点。在此，有报道称与Z环相关的蛋白ZapA和ZapB在细胞中部形成不依赖于FtsZ的结构。在FtsZ聚合拮抗剂SulA破坏Z环后，ZapA仍作为云状聚集体留在细胞中部。使用与FtsZ相互作用有缺陷的变体ZapA(N60Y)，证实这些ZapA结构的形成与Z环没有联系。此外，GFP-ZapA(N60Y)在细胞中部的积累通常先于Z环，并且需要ZapB来组装，这表明ZapB聚合物构成了这些结构的基础。在没有MatP（一种将ZapB与染色体末端区域连接起来的DNA结合蛋白）的情况下，云状的ZapA结构仍然形成，但未能与染色体末端同步，并且在细胞中部并不总是先于FtsZ出现。综上所述，结果表明ZapA-ZapB的不依赖于FtsZ的结构为Z环的形成提供了额外的位置线索，并可能有助于协调其组装与染色体复制和分离。
