Crystal structure of Tam41 cytidine diphosphate diacylglycerol synthase from a Firmicutes bacterium
Crystal structure of Tam41 cytidine diphosphate diacylglycerol synthase from a Firmicutes bacterium
复制标题
DOI：
10.1093/jb/mvab154
复制
发表时间：
2022-04-01
影响因子：
2.7
通讯作者：
Tamura, Yasushi
中科院分区：
文献类型：
--
作者：
Kimura, Keisuke;Kawai, Fumihiro;Tamura, Yasushi
转运子组装和维护41(Tam41)催化合成胞苷二磷酸二酰甘油(CDP-DAG)，这是一种在线粒体中产生心磷脂的高能中间磷脂。虽然Tam41几乎只存在于真核细胞中，但Firmicuts细菌含有编码Tam41型CDP-DAG合成酶(FbTam41)的基因。FbTam41在体外以三元络合机制将磷脂酸(PA)转化为CDP-DAG。此外，FbTam41在体内对酵母Tam41进行了功能取代。这些结果表明Tam41型CDP-DAG合成酶在一些原核细胞中具有功能。我们测定了FbTam41的晶体结构，在2.6A的分辨率下，缺少胞苷三磷酸(CTP)-镁离子结合形式的C-末端18个残基。晶体结构表明，FbTam41含有一个带正电荷的口袋，该口袋专门与CTP-镁离子和PA紧密结合。利用这种结构，我们构建了FbTam41的全长结构模型，该结构包含晶体结构中缺失的最后一个a-螺旋。基于这一模型，我们提出了细菌细胞和线粒体合成CDP-DAG的分子机制。
Translocator assembly and maintenance 41 (Tam41) catalyses the synthesis of cytidine diphosphate diacylglycerol (CDP-DAG), which is a high-energy intermediate phospholipid critical for generating cardiolipin in mitochondria. Although Tam41 is present almost exclusively in eukaryotic cells, a Firmicutes bacterium contains the gene encoding Tam41-type CDP-DAG synthase (FbTam41). FbTam41 converted phosphatidic acid (PA) to CDP-DAG using a ternary complex mechanism in vitro. Additionally, FbTam41 functionally substituted yeast Tam41 in vivo. These results demonstrate that Tam41-type CDP-DAG synthase functions in some prokaryotic cells. We determined the crystal structure of FbTam41 lacking the C-terminal 18 residues in the cytidine triphosphate (CTP)-Mg2+ bound form at a resolution of 2.6 A. The crystal structure showed that FbTam41 contained a positively charged pocket that specifically accommodated CTP-Mg2+ and PA in close proximity. By using this structure, we constructed a model for the full-length structure of FbTam41 containing the last a-helix, which was missing in the crystal structure. Based on this model, we propose a molecular mechanism for CDP-DAG synthesis in bacterial cells and mitochondria.