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Crystal structure of EXD2 exonuclease domain
Structural highlights
FunctionEXD2_HUMAN Exonuclease required for double-strand breaks resection and efficient homologous recombination. Plays a key role in controlling the initial steps of chromosomal break repair, it is recruited to chromatin in a damage-dependent manner and functionally interacts with the MRN complex to accelerate resection through its 3'-5' exonuclease activity, which efficiently processes double-stranded DNA substrates containing nicks.[1] [2] Publication Abstract from PubMedEXD2 (3'-5' exonuclease domain-containing protein 2) is an essential protein with a conserved DEDDy superfamily 3'-5' exonuclease domain. Recent research suggests that EXD2 has two potential functions: as a component of the DNA double-strand break repair machinery and as a ribonuclease for the regulation of mitochondrial translation. Herein, electron microscope imaging analysis and proximity labeling revealed that EXD2 is anchored to the mitochondrial outer membrane through a conserved N-terminal transmembrane domain, while the C-terminal region is cytosolic. Crystal structures of the exonuclease domain in complex with Mn2+/Mg2+ revealed a domain-swapped dimer in which the central alpha5-alpha7 helices are mutually crossed over, resulting in chimeric active sites. Additionally, the C-terminal segments absent in other DnaQ family exonucleases enclose the central chimeric active sites. Combined structural and biochemical analyses demonstrated that the unusual dimeric organization stabilizes the active site, facilitates discrimination between DNA and RNA substrates based on divalent cation coordination and generates a positively charged groove that binds substrates. The structure of human EXD2 reveals a chimeric 3' to 5' exonuclease domain that discriminates substrates via metal coordination.,Park J, Lee SY, Jeong H, Kang MG, Van Haute L, Minczuk M, Seo JK, Jun Y, Myung K, Rhee HW, Lee C Nucleic Acids Res. 2019 Jul 26;47(13):7078-7093. doi: 10.1093/nar/gkz454. PMID:31127291[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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