Straume Daniel, Stamsås Gro Anita, Berg Kari Helene, Salehian Zhian, Håvarstein Leiv Sigve
Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Ås, NO-1432, Norway.
Mol Microbiol. 2017 Jan;103(1):99-116. doi: 10.1111/mmi.13543. Epub 2016 Oct 27.
The oval shape of pneumococci results from a combination of septal and lateral peptidoglycan synthesis. The septal cross-wall is synthesized by the divisome, while the elongasome drives cell elongation by inserting new peptidoglycan into the lateral cell wall. Each of these molecular machines contains penicillin-binding proteins (PBPs), which catalyze the final stages of peptidoglycan synthesis, plus a number of accessory proteins. Much effort has been made to identify these accessory proteins and determine their function. In the present paper we have used a novel approach to identify members of the pneumococcal elongasome that are functionally closely linked to PBP2b. We discovered that cells depleted in PBP2b, a key component of the elongasome, display several distinct phenotypic traits. We searched for proteins that, when depleted or deleted, display the same phenotypic changes. Four proteins, RodA, MreD, DivIVA and Spr0777, were identified by this approach. Together with PBP2b these proteins are essential for the normal function of the elongasome. Furthermore, our findings suggest that DivIVA, which was previously assigned as a divisomal protein, is required to correctly localize the elongasome at the negatively curved membrane region between the septal and lateral cell wall.
肺炎球菌的椭圆形是由隔膜和侧向肽聚糖合成共同作用的结果。隔膜横壁由分裂体合成，而伸长体通过将新的肽聚糖插入侧向细胞壁来驱动细胞伸长。这些分子机器中的每一个都包含青霉素结合蛋白（PBPs），其催化肽聚糖合成的最后阶段，以及一些辅助蛋白。人们已经付出了很多努力来鉴定这些辅助蛋白并确定它们的功能。在本文中，我们采用了一种新方法来鉴定肺炎球菌伸长体中与PBP2b功能密切相关的成员。我们发现，伸长体的关键成分PBP2b缺失的细胞表现出几种不同的表型特征。我们寻找那些在缺失或删除时表现出相同表型变化的蛋白质。通过这种方法鉴定出了四种蛋白质，即RodA、MreD、DivIVA和Spr0777。这些蛋白质与PBP2b一起对伸长体的正常功能至关重要。此外，我们的研究结果表明，以前被归类为分裂体蛋白的DivIVA是将伸长体正确定位在隔膜和侧向细胞壁之间负曲率膜区域所必需的。
