Structures of the Mitochondrial CDP-DAG Synthase Tam41 Suggest a Potential Lipid Substrate Pathway from Membrane to the Active Site

• Published in: Structure (London) 2019-08, Vol.27 (8), p.1258-1269.e4
• Main Authors: Jiao, Haizhan, Yin, Yan, Liu, Zhenfeng
• Format: Article
• Language: English
• Subjects: amphipathic helix; cardiolipin; Catalytic Domain; CDP-diacylglycerol; Cell Membrane - metabolism; Cytidine Triphosphate - metabolism; Diacylglycerol Cholinephosphotransferase - chemistry; Diacylglycerol Cholinephosphotransferase - metabolism; Fungal Proteins - chemistry; Fungal Proteins - metabolism; Lipid Metabolism; mitochondrial membrane; Mitochondrial Proteins - chemistry; Mitochondrial Proteins - metabolism; Models, Molecular; nucleotidyltransferase fold; phosphatidic acid; phospholipid biosynthesis; Protein Conformation; Schizosaccharomyces - chemistry; Schizosaccharomyces - metabolism; structure; Substrate Specificity; Tam41; winged helix domain
• ISSN: 0969-2126; 1878-4186
• DOI: 10.1016/j.str.2019.04.017

In mitochondria, CDP-diacylglycerol (CDP-DAG) is a crucial precursor for cardiolipin biosynthesis. Mitochondrial CDP-DAG is synthesized by the translocator assembly and maintenance protein 41 (Tam41) through an elusive process. Here we show that Tam41 adopts sequential catalytic mechanism, and report crystal structures of the bulk N-terminal region of Tam41 from Schizosaccharomyces pombe in the apo and CTP-bound state. The structure reveals that Tam41 contains a nucleotidyltransferase (NTase) domain and a winged helix domain. CTP binds to an “L”-shaped pocket sandwiched between the two domains. Rearrangement of a loop region near the active site is essential for opening the CTP-binding pocket. Docking of phosphatidic acid/CDP-DAG in the structure suggests a lipid entry/exit pathway connected to the “L”-shaped pocket. The C-terminal region of SpTam41 contains a positively charged amphipathic helix crucial for membrane association and participates in binding phospholipids. These results provide detailed insights into the mechanism of CDP-DAG biosynthesis in mitochondria. [Display omitted] •Structure of Tam41 reveals an NTase domain fused with a winged helix domain•CTP binds to an “L”-shaped active-site pocket sandwiched between two domains•The C-terminal amphipathic helices mediate the association of Tam41 with membrane•A potential pathway connects the active site with the membrane for lipid entry/exit Jiao et al. report the structure of mitochondrial CDP-diacylglycerol synthase Tam41 and reveal the CTP-binding active site sandwiched between a nucleotidyltransferase domain and a winged helix domain. The C-terminal region of Tam41 contains an amphipathic helix involved in membrane association. Detailed insights into the pathway for lipid entry/exit are obtained.