Thymine DNA glycosylase exhibits negligible affinity for nucleobases that it removes from DNA.
作者： Shuja S. Malik , Christopher T. Coey , Kristen M. Varney , Edwin Pozharski , Alexander C. Drohat
DOI: 10.1093/NAR/GKV890
关键词:
摘要: Thymine DNA Glycosylase (TDG) performs essential functions in maintaining genetic integrity and epigenetic regulation. Initiating base excision repair, TDG removes thymine from mutagenic G ·: T mispairs caused by 5-methylcytosine (mC) deamination other lesions including uracil (U) 5-hydroxymethyluracil (hmU). In demethylation, excises 5-formylcytosine (fC) 5-carboxylcytosine (caC), which are generated mC Tet (ten-eleven translocation) enzymes. Using improved crystallization conditions, we solved high-resolution (up to 1.45 A) structures of enzyme-product complexes substrates G·U, G·T, G·hmU, G·fC G·caC. The reveal many new features, key water-mediated enzyme-substrate interactions. Together with nuclear magnetic resonance experiments, the demonstrate that releases excised its tight product complex abasic DNA, contrary previous reports. Moreover, DNA-free exhibits no significant binding free nucleobases (U, T, hmU), indicating a Kd >> 10 mM. solvent-filled channel active site, might facilitate dissociation enable caC excision, involves solvent-mediated acid catalysis. Dissociation allows bind beta rather than alpha anomer sugar, stabilize complex.
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