College of Chemistry, Beijing Normal University, Beijing, 100875, China.
Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, K7L 3N6, Canada.
Sci Rep. 2017 Aug 8;7(1):7627. doi: 10.1038/s41598-017-08213-5.
Proper cell division at the mid-site of Gram-negative bacteria reflects stringent regulation by the min system (MinC, MinD and MinE). Herein we report crystal structure of the C-terminal domain of MinC from Escherichia coli (EcMinC). The MinC beta helical domain is engaged in a tight homodimer, similar to Thermotoga maritima MinC (TmMinC). However, both EcMinC and TmMinC lack an α-helix (helix3) at their C-terminal tail, in comparison to Aquifex aerolicu MinC (AaMinC) which forms an extra interaction interface with MinD. To understand the role of this extra binding element in MinC/MinD interactions, we fused this helix (Aahelix3) to the C-terminus of EcMinC and examined its effect on cell morphology and cell growth. Our results revealed that Aahelix3 impaired normal cell division in vivo. Furthermore, results of a co-pelleting assay and binding free energy calculation suggested that Aahelix3 plays an essential role in AaMinCD complex formation, under the circumstance of lacking MinE in A. aerolicu. Combining these results with sequence analysis of MinC and MinD in different organisms, we propose an evolutionary relationship to rationalize different mechanisms in cell division positioning in various organisms.
革兰氏阴性菌中位点恰当的细胞分裂反映了 Min 系统（MinC、MinD 和 MinE）的严格调控。在此，我们报告了来自大肠杆菌（EcMinC）的 MinC C 端结构域的晶体结构。MinC 的β螺旋结构域形成紧密的同源二聚体，类似于海洋栖热菌 MinC（TmMinC）。然而，与 Aquifex aerolicus MinC（AaMinC）相比，EcMinC 和 TmMinC 都缺少 C 端尾部的α-螺旋（螺旋 3），后者与 MinD 形成额外的相互作用界面。为了了解该额外结合元件在 MinC/MinD 相互作用中的作用，我们将该螺旋（Aahelix3）融合到 EcMinC 的 C 端，并研究其对细胞形态和细胞生长的影响。我们的结果表明，Aahelix3 在体内损害了正常的细胞分裂。此外，共沉淀测定和结合自由能计算的结果表明，在 Aeropyrum pernix 中缺乏 MinE 的情况下，Aahelix3 在 AaMinCD 复合物形成中发挥了重要作用。将这些结果与不同生物体中 MinC 和 MinD 的序列分析相结合，我们提出了一种进化关系来合理化不同生物体中细胞分裂定位的不同机制。
