A mutant of uracil DNA glycosylase that distinguishes between cytosine and 5-methylcytosine.
basic_science · Level V
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- Record sourced from PubMed, PMID 24740413.
- Also identified by DOI 10.1371/journal.pone.0095394 and PMC identifier 3989344.
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Abstract
We demonstrate that a mutant of uracil DNA glycosylase (N123D:L191A) distinguishes between cytosine and methylcytosine. Uracil DNA glycosylase (UDG) efficiently removes uracil from DNA in a reaction in which the base is flipped into the enzyme's active site. Uracil is selected over cytosine by a pattern of specific hydrogen bonds, and thymine is excluded by steric clash of its 5-methyl group with Y66. The N123D mutation generates an enzyme that excises cytosine. This N123D:L191A mutant excises C when it is mispaired with A or opposite an abasic site, but not when it is paired with G. In contrast no cleavage is observed with any substrates that contain 5-methylcytosine. This enzyme may offer a new approach for discriminating between cytosine and 5-methylcytosine.
Medical subject headings
- 5-Methylcytosine
- Bacterial Proteins
- Cytosine
- Escherichia coli
- Mutation
- Uracil-DNA Glycosidase