School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China.
School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China; Department of Psychological and Brain Sciences, Dartmouth College, Hanover, NH 03755, USA.
J Mol Biol. 2024 Oct 15;436(20):168750. doi: 10.1016/j.jmb.2024.168750. Epub 2024 Aug 20.
The final step in the de novo synthesis of cytidine 5'-triphosphate (CTP) is catalyzed by CTP synthase (CTPS), which can form cytoophidia in all three domains of life. Recently, we have discovered that CTPS binds to ribonucleotides (NTPs) to form filaments, and have successfully resolved the structures of Drosophila melanogaster CTPS bound with NTPs. Previous biochemical studies have shown that CTPS can bind to deoxyribonucleotides (dNTPs) to produce 2'-deoxycytidine-5'-triphosphate (dCTP). However, the structural basis of CTPS binding to dNTPs is still unclear. In this study, we find that Drosophila CTPS can also form filaments with dNTPs. Using cryo-electron microscopy, we are able to resolve the structure of Drosophila melanogaster CTPS bound to dNTPs with a resolution of up to 2.7 Å. By combining these structural findings with biochemical analysis, we compare the binding and reaction characteristics of NTPs and dNTPs with CTPS. Our results indicate that the same enzyme can act bifunctionally as CTP/dCTP synthase in vitro, and provide a structural basis for these activities.
三磷酸胞苷（CTP）从头合成的最后一步由 CTP 合酶（CTPS）催化，该酶可以在所有三个生命领域形成细胞丝状伪足。最近，我们发现 CTPS 与核苷酸（NTPs）结合形成纤维，并且已经成功解析了与 NTPs 结合的黑腹果蝇 CTPS 的结构。以前的生化研究表明，CTPS 可以与脱氧核苷酸（dNTPs）结合生成 2'-脱氧胞苷-5'-三磷酸（dCTP）。然而，CTPS 与 dNTPs 结合的结构基础仍不清楚。在这项研究中，我们发现 Drosophila CTPS 也可以与 dNTPs 形成纤维。通过使用冷冻电镜，我们能够解析出分辨率高达 2.7Å 的与 dNTP 结合的黑腹果蝇 CTPS 的结构。通过将这些结构发现与生化分析相结合，我们比较了 NTPs 和 dNTPs 与 CTPS 的结合和反应特性。我们的结果表明，相同的酶在体外可以发挥 CTP/dCTP 合酶的双重功能，并为这些活性提供了结构基础。
