Linked Life Data

19880517

Source:http://linkedlifedata.com/resource/pubmed/id/19880517

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
52
pubmed:dateCreated
2009-12-21
pubmed:abstractText
Thymine DNA glycosylase (TDG) promotes genomic integrity by excising thymine from mutagenic G.T mismatches arising by deamination of 5-methylcytosine, and follow-on base excision repair enzymes restore a G.C pair. TDG cleaves the N-glycosylic bond of dT and some other nucleotides, including 5-substituted 2'-deoxyuridine analogs, once they have been flipped from the helix into its active site. We examined the role of two strictly conserved residues; Asn(140), implicated in the chemical step, and Arg(275), implicated in nucleotide flipping. The N140A variant binds substrate DNA with the same tight affinity as wild-type TDG, but it has no detectable base excision activity for a G.T substrate, and its excision rate is vastly diminished (by approximately 10(4.4)-fold) for G.U, G.FU, and G.BrU substrates. Thus, Asn(140) does not contribute substantially to substrate binding but is essential for the chemical step, where it stabilizes the transition state by approximately 6 kcal/mol (compared with 11.6 kcal/mol stabilization provided by TDG overall). Our recent crystal structure revealed that Arg(275) penetrates the DNA minor groove, filling the void created by nucleotide flipping. We found that the R275A and R275L substitutions weaken substrate binding and substantially decrease the base excision rate for G.T and G.BrU substrates. Our results indicate that Arg(275) promotes and/or stabilizes nucleotide flipping, a role that is most important for target nucleotides that are relatively large (dT and bromodeoxyuridine) and/or have a stable N-glycosylic bond (dT). Arg(275) does not contribute substantially to the binding of TDG to abasic DNA product, and it cannot account for the slow product release exhibited by TDG.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Dec
pubmed:issn
1083-351X
pubmed:author
pubmed:issnType
Electronic
pubmed:day
25
pubmed:volume
284
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
36680-8
pubmed:dateRevised
2011-1-24
pubmed:meshHeading
pubmed:year
2009
pubmed:articleTitle
Role of two strictly conserved residues in nucleotide flipping and N-glycosylic bond cleavage by human thymine DNA glycosylase.
pubmed:affiliation
Department of Biochemistry and Molecular Biology, Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't, Research Support, N.I.H., Extramural