Bahloul A, Meury J, Kern R, Garwood J, Guha S, Kohiyama M
Institut Jacques Monod, Université Paris, France.
Mol Microbiol. 1996 Oct;22(2):275-82. doi: 10.1046/j.1365-2958.1996.00106.x.
oriC DNA in the hemimethylated (but not in the fully methylated) state reacts with an Escherichia coli K-12 outer membrane preparation. This reaction is drastically reduced when the membrane preparation of a seqA null mutant is used. An in vitro reconstitution of the activity was undertaken by adding a partially purified SeqA protein to a seqA mutant membrane without success. A possible reason for this failure might be a profound modification of the outer membrane of the seqA mutant (as revealed by the fact that membrane from the mutant sediments more slowly than that from the wild type during ultracentrifugation). There is also a reduction in the content of OmpF protein. Moreover, one of the minor outer membrane proteins involved in partitioning of newly synthesized chromosomes, the ToiC (MukA) protein, was also found to be downregulated in the seqA mutant. This is also true of the hobH mutant grown in a high-osmolarity medium. Mutants of both seqA and hobH stop dividing after hyperosmotic shock, forming filaments (as observed in dam mutants).
处于半甲基化状态（而非完全甲基化状态）的oriC DNA与大肠杆菌K - 12外膜制剂发生反应。当使用seqA缺失突变体的膜制剂时，这种反应会大幅降低。通过向seqA突变体膜中添加部分纯化的SeqA蛋白进行了该活性的体外重建，但未成功。失败的一个可能原因可能是seqA突变体的外膜发生了深刻的修饰（超离心过程中突变体的膜比野生型的膜沉降得更慢这一事实揭示了这一点）。OmpF蛋白的含量也有所减少。此外，在新合成染色体分配过程中涉及的一种次要外膜蛋白ToiC（MukA）蛋白，在seqA突变体中也被发现表达下调。在高渗培养基中生长的hobH突变体也是如此。seqA和hobH的突变体在高渗休克后停止分裂，形成细丝（如在dam突变体中观察到的那样）。
