4z47

Structure of the enzyme-product complex resulting from TDG action on a GU mismatch in the presence of excess baseStructure of the enzyme-product complex resulting from TDG action on a GU mismatch in the presence of excess base

Structural highlights 4z47 is a 3 chain structure with sequence from Homo sapiens and Synthetic construct. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 1.45Å Ligands: , , Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function TDG_HUMAN In the DNA of higher eukaryotes, hydrolytic deamination of 5-methylcytosine to thymine leads to the formation of G/T mismatches. This enzyme corrects G/T mispairs to G/C pairs. It is capable of hydrolyzing the carbon-nitrogen bond between the sugar-phosphate backbone of the DNA and a mispaired thymine. In addition to the G/T, it can remove thymine also from C/T and T/T mispairs in the order G/T >> C/T > T/T. It has no detectable activity on apyrimidinic sites and does not catalyze the removal of thymine from A/T pairs or from single-stranded DNA. It can also remove uracil and 5-bromouracil from mispairs with guanine. Publication Abstract from PubMed 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 and other lesions including uracil (U) and 5-hydroxymethyluracil (hmU). In DNA demethylation, TDG excises 5-formylcytosine (fC) and 5-carboxylcytosine (caC), which are generated from mC by Tet (ten-eleven translocation) enzymes. Using improved crystallization conditions, we solved high-resolution (up to 1.45 A) structures of TDG enzyme-product complexes generated from substrates including G.U, G.T, G.hmU, G.fC and G.caC. The structures reveal many new features, including key water-mediated enzyme-substrate interactions. Together with nuclear magnetic resonance experiments, the structures demonstrate that TDG releases the excised base from its tight product complex with abasic DNA, contrary to previous reports. Moreover, DNA-free TDG exhibits no significant binding to free nucleobases (U, T, hmU), indicating a Kd >> 10 mM. The structures reveal a solvent-filled channel to the active site, which might facilitate dissociation of the excised base and enable caC excision, which involves solvent-mediated acid catalysis. Dissociation of the excised base allows TDG to bind the beta rather than the alpha anomer of the abasic sugar, which might stabilize the enzyme-product complex. Thymine DNA glycosylase exhibits negligible affinity for nucleobases that it removes from DNA.,Malik SS, Coey CT, Varney KM, Pozharski E, Drohat AC Nucleic Acids Res. 2015 Sep 10. pii: gkv890. PMID:26358812 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also DNA glycosylase 3D structures

spinqualitylabelsall models 4z47, resolution 1.45Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image