9ky4
From Proteopedia
Cryo-EM structure of the mono-DdCBE bound TS substrate complex.
Structural highlights
FunctionDDDA_BURC1 Toxic component of a toxin-immunity protein module, which functions as a cellular contact-dependent growth inhibition (CDI) system. CDI modules allow bacteria to communicate with and inhibit the growth of closely related neighboring bacteria in a contact-dependent fashion. Bacteria that have this module inhibit or kill bacteria without it, giving them a growth advantage. Probably specifically inhibited by cognate immunity protein DddI (Probable). The C-terminal 163 residue fragment has double-stranded DNA cytidine deaminase activity; it does not deaminate ssDNA, ssRNA or dsRNA. Leads to C:G to T:A conversions in deaminated DNA. Preferentially deaminates 5'-TC-3' substrates (PubMed:32641830).[1] Publication Abstract from PubMedDddA-derived cytosine base editor (DdCBE) couples transcription activator-like effector (TALE) arrays and the double-stranded DNA (dsDNA)-specific cytidine deaminase DddA to target mitochondrial DNA (mtDNA) for editing. However, structures of DdCBE in action are unavailable, impeding its mechanistic-based optimization for high-precision-demanding therapeutic applications. Here, we determined the cryo-electron microscopy (cryo-EM) structures of DdCBE targeting two native mitochondrial gene loci and combined editing data from systematically designed spacers to develop WinPred, a model that can predict DdCBE's editing outcome and guide its design to achieve high-precision editing. Furthermore, structure-guided engineering of DddA narrowed the editing window of DdCBE to 2-3 nt while minimizing its off-target (OT) editing to near-background levels, thereby generating accurate DdCBE (aDdCBE). Using aDdCBE, we precisely introduced a Leber hereditary optic neuropathy (LHON)-disease-related mutation into mtDNA and faithfully recapitulated the pathogenic conditions without interference from unintended bystander or OT mutations. Our work provides a mechanistic understanding of DdCBE and establishes WinPred and aDdCBE as useful tools for faithfully modeling or correcting disease-related mtDNA mutations. Structural insights into DdCBE in action enable high-precision mitochondrial DNA editing.,Xiang J, Xu W, Wu J, Luo Y, Liu C, Hou Y, Chen J, Yang B Mol Cell. 2025 Sep 18;85(18):3357-3372.e9. doi: 10.1016/j.molcel.2025.08.016. , Epub 2025 Sep 10. PMID:40934924[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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