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Catalytic Site Atlas Version 2.2.12
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CSA entry for 1mug
Original Entry
G:t/u specific dna glycosylase
EC Class:
Other CSA Entries:
Overview of all sites for 1mug
Homologues of 1mug
Entries for UniProt/Swiss-Prot: P43342
Entries for EC: 3.2.2.-
Other Databases:
PDB entry: 1mug
PDBsum entry: 1mug
UniProt/Swiss-Prot: P43342
IntEnz entry: 3.2.2.-
Literature Report:
Mismatched base pairing between G and U or G and T is common in DNA replication and would lead to substitution mutations. Therefore the enzyme G:T/U MISMATCH-SPECIFIC DNA GLYCOSYLASE is vital in preserving the integrity of DNA: it is able to hydrolyse the glycosidic bond to release the uracil or thymine base, thus creating an abasic site which allows the entire nucleotide to be recognised and removed. The enzyme shows significant structural and functional similarity to the well characterised family of Uracil DNA glycosylases which remove uracil wherever it occurs in DNA; however there is very little sequence similarity suggesting that convergent evolution may be responsible for the similarities observed.
The mechanism proceeds via the attack of a nucleophilic water molecule on the carbon atom of the glycosidic bond. Activation of the water molecule is achieved by Asn 18's electrostatic interactions with the lone pair and hydrogen atom of the water. The uracil moiety then acts as the leaving group, abstracting a proton from the attacking water molecule. This reaction mechanism therefore is slow compared to the general acid/general base mechanism employed by the UDG family.

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Literature reference 

ResidueChainNumberUniProt numberFunctional part FunctionTargetDescription
ASNA 18 18Sidechain
Activates water to allow it to act as a nucleophile and attack the glycosidic bond.
Evidence from paper Evidence concerns Evidence type
PubMed ID 9489705 Current protein Conservation of residue
PubMed ID 9489705 Current protein Residue is positioned appropriately (ligand position known)
Crystal structure of a G:T/U mismatch-specific DNA glycosylase: mismatch recognition by complementary-strand interactions.
T. E. Barrett and R. Savva and G. Panayotou and T. Barlow and T. Brown and J. Jiricny and L. H. Pearl
Cell 92, (1) 117-29, (1998).
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