Separating substrate recognition from base hydrolysis in human thymine DNA glycosylase by mutational analysis

Hardeland, Ulrike and Bentele, Marc and Jiricny, Josef and Schär, Primo. (2000) Separating substrate recognition from base hydrolysis in human thymine DNA glycosylase by mutational analysis. Journal of biological chemistry, Vol. 275, H. 43. pp. 33449-33456.

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Official URL: http://edoc.unibas.ch/dok/A5254007

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Human thymine DNA glycosylase (TDG) was discovered as an enzyme that can initiate base excision repair at sites of 5-methylcytosine- or cytosine deamination in DNA by its ability to release thymine or uracil from G.T and G.U mismatches. Crystal structure analysis of an Escherichia coli homologue identified conserved amino acid residues that are critical for its substrate recognition/interaction and base hydrolysis functions. Guided by this revelation, we performed a mutational study of structure function relationships with the human TDG. Substitution of the postulated catalytic site asparagine with alanine (N140A) resulted in an enzyme that bound mismatched substrates but was unable to catalyze base removal. Mutation of Met-269 in a motif with a postulated role in protein-substrate interaction selectively inactivated stable binding of the enzyme to mismatched substrates but not so its glycosylase activity. These results establish that the structure function model postulated for the E. coli enzyme is largely applicable to the human TDG. We further provide evidence for G.U being the preferred substrate of TDG, not only at the mismatch recognition step of the reaction but also in base hydrolysis, and for the importance of stable complementary strand interactions by TDG to compensate for its comparably poor hydrolytic potential.
Faculties and Departments:03 Faculty of Medicine > Departement Biomedizin > Division of Biochemistry and Genetics > Molecular Genetics (Schär)
UniBasel Contributors:Schär, Primo Leo
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:American Society of Biological Chemists
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:22 Mar 2012 14:23
Deposited On:22 Mar 2012 13:34

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