Intercell AG, Vienna Biocenter 3, A-1030 Vienna, Austria.
Microbiology (Reading). 2010 Jun;156(Pt 6):1697-1707. doi: 10.1099/mic.0.036335-0. Epub 2010 Mar 11.
The importance of serine/threonine phosphorylation in signalling and regulation of gene expression in prokaryotes has been widely recognized. Driven by our interest in StkP (the pneumococcal serine/threonine kinase homologue) for vaccine development, we studied its cellular localization. We found that the C-terminally located PASTA (penicillin-binding protein and serine/threonine kinase associated) domains, but not the N-terminal kinase domain of StkP, were located on the surface of live pneumococcal cells grown in vitro and were also accessible to antibodies during pneumococcal infection in mice and man. Most importantly, we discovered, by immunofluorescence microscopy, that StkP co-localized with the cell division apparatus. StkP and FtsZ, the prokaryotic tubulin homologue, co-localized at mid-cell in most cells. Formation and constriction of the ring-like structure of StkP followed the dynamic changes of FtsZ in dividing cells. This pattern resembles that of the 'late' divisome protein penicillin-binding protein 2X. The lack of StkP in gene deletion mutants did not disturb FtsZ ring formation, further suggesting that StkP joins the divisome after the FtsZ ring is assembled. We also present evidence that StkP binds and phosphorylates recombinant FtsZ in vitro; however, we could not detect changes in the phosphorylation of FtsZ in a stkP deletion strain relative to wild-type cells. Based on its cell-division-dependent localization and interaction with FtsZ, we propose that StkP plays a currently undefined role in cell division of pneumococcus.
丝氨酸/苏氨酸磷酸化在原核生物信号转导和基因表达调控中的重要性已得到广泛认可。受我们对 StkP（肺炎球菌丝氨酸/苏氨酸激酶同源物）用于疫苗开发的兴趣的驱动，我们研究了其细胞定位。我们发现，位于 C 端的 PASTA（青霉素结合蛋白和丝氨酸/苏氨酸激酶相关）结构域，但不是 StkP 的 N 端激酶结构域，位于体外生长的活肺炎球菌细胞表面，并且在小鼠和人类肺炎球菌感染期间也可被抗体识别。最重要的是，我们通过免疫荧光显微镜发现，StkP 与细胞分裂装置共定位。在大多数细胞中，StkP 和原核微管蛋白同源物 FtsZ 在中部分布。StkP 环样结构的形成和收缩与分裂细胞中 FtsZ 的动态变化相吻合。这种模式类似于“晚期”分裂体蛋白青霉素结合蛋白 2X 的模式。在基因缺失突变体中缺乏 StkP 不会干扰 FtsZ 环的形成，这进一步表明 StkP 在 FtsZ 环组装后加入分裂体。我们还提供了证据表明，StkP 在体外结合并磷酸化重组 FtsZ；然而，与野生型细胞相比，我们无法检测到 stkP 缺失菌株中 FtsZ 磷酸化的变化。基于其细胞分裂依赖性定位和与 FtsZ 的相互作用，我们提出 StkP 在肺炎球菌的细胞分裂中发挥着目前尚未定义的作用。
