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SYSTEMATIC NAME
IUBMB Comments
uracil-double-stranded DNA deoxyribohydrolase (uracil-releasing)
No activity on DNA containing a T/G mispair or single-stranded DNA containing either a site-specific uracil or 3,N4-ethenocytosine residue [2], significant role for double-stranded uracil-DNA glycosylase in mutation avoidance in non-dividing E. coli [3]. Uracil-DNA glycosylases are widespread enzymes that are found in all living organisms. Uracil-DNA glycosylase (EC 3.2.2.27) and EC 3.2.2.28 form a central part of the DNA-repair machinery since they initiate the DNA base-excision repair pathway by hydrolysing the N-glycosidic bond between uracil and the deoxyribose sugar thereby catalysing the removal of mis-incorporated uracil from DNA.
the enzyme excised both 3,N4-ethenocytosine and uracil from DNA. 3,N4-ethenocytosine is significantly better as a substrate in terms of binding and hydrolysis. The tighter binding of the 3,N4-ethenocytosine containing substrate by MUG probably also accounts for its activity against single-stranded DNA containing 3,N4-ethenocytosine. Cleavage of the single-stranded substrate is 1500fold slower than the double-stranded substrate
the enzyme excised both 3,N4-ethenocytosine and uracil from DNA. 3,N4-ethenocytosine is significantly better as a substrate in terms of binding and hydrolysis. The tighter binding of the 3,N4-ethenocytosine containing substrate by MUG probably also accounts for its activity against single-stranded DNA containing 3,N4-ethenocytosine. Cleavage of the single-stranded substrate is 1500fold slower than the double-stranded substrate. Of the different substrates tested, a duplex containing the 3,N4-ethenocytosine pair has the highest affinity for the enzyme, U/G is the next best substrate
Dug is active on duplex oligonucleotides (34-mers) that contain site-specific U/G or U/A mismatches. Dug excises a near stoichiometric amount of uracil from U/G-containing oligonucleotide substrate. The lack of turnover is the result of strong binding by Dug to the reaction product apyrimidinic-site
the enzyme activity against the uracil-containing single-stranded DNA is so low that it is not likely to be of any significance. Of the different substrates tested, a duplex containing the 3,N4-ethenocytosine pair has the highest affinity for the enzyme, U/G is the next best substrate
Mug is expressed poorly in exponentially growing cells and has no apparent role in mutation avoidance in these cells. Mug is fairly abundant in stationary-phase cells and has an important anti-mutator role at this stage of cell growth
5-Hydroxyuracil and inosine (hypoxanthine) show cleavage rates 2–3 orders of magnitude slower than 3,N4-ethenocytosine. Thymine, 5-hydroxymethyluracil, and 5-hydroxycytosine are cleaved to some extent, although extremely slowly
activity is not detected on DNA containing a T/G mispair or single-stranded DNA containing either a site-specific uracil or 3,N4-ethenocytosine residue. Endonuclease IV stimulates Dug activity by enhancing the rate and extent of uracil excision by promoting dissociation of Dug from the apyrimidinic-site/G-containing 34-mer. Catalytically active endonuclease IV is required to mediate Dug turnover
UdgB substrate specificity with diverse DNA oligomers, overview, the enzyme excises ethenocytosine and hypoxanthine from dsDNA, in addition to uracil present as a single-nucleotide bulge in dsDNA, but excision of 5-OH-C, dihydroxyuracil, and epsilonA is undetectable, MtuUdgB does not excise uracil from SSU9 ssDNA, mechanism of action, overview
the enzyme showed no activity on oxanine-containing DNA substrates, uracil-mismatched single-stranded DNA and hypoxanthine-mismatched single-stranded DNA
Mug is expressed poorly in exponentially growing cells and has no apparent role in mutation avoidance in these cells. Mug is fairly abundant in stationary-phase cells and has an important anti-mutator role at this stage of cell growth
UdgB inhibition by dsDNA containing AP-site in the uracil-containing single-nucleotide bulge, UgdB is insensitive against UDG inhibition protein from Bacillus subtilis and shows no inhibition by uracil
endonuclease IV stimulates Dug activity by enhancing the rate and extent of uracil excision by promoting dissociation of Dug from the apyrimidinic-site/G-containing 34-mer. Catalytically active endonuclease IV is required to mediate Dug turnover
poorly expressed in exponentially growing cells. Mug is overexpressed as cells enter stationary phase, and it is maintained at a fairly high level in resting cells. This is true of cells grown in rich or minimal media, and the principal regulation of mug is at the level of mRNA. Although the expression of mug is strongly dependent on the stationary-phase sigma factor, when cells are grown in minimal media, it shows only a modest dependence on stationary-phase sigma factor when cells are grown in rich media
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Crystallization/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
crystal structure of the Escherichia coli MUG enzyme complexed with an oligonucleotide containing a non-hydrolysable deoxyuridine analogue mismatched with guanine
crystal structures of the mismatch-specific uracil DNA-glycosylase from Escherichia coli, and of a DNA complex, reveal a remarkable structural and functional homology to UDGs despite low sequence identity
gene Rv1259, DNA and amino aid sequence determination and analysis, cloning and overexpression of His6-tagged wild-type and mutant enzymes in Escherichia coli strains
Mosbaugh, D.W.: Escherichia coli double-strand uracil-DNA glycosylase: involvement in uracil-mediated DNA base excision repair and stimulation of activity by endonuclease IV
3,N4-ethenocytosine, a highly mutagenic adduct, is a primary substrate for Escherichia coli double-stranded uracil-DNA glycosylase and human mismatch-specific thymine-DNA glycosylase