Year: 2004
Type: article
Abstract: The Escherichia coli adenine DNA glycosylase, MutY, plays an important role in the maintenance of genomic stability by catalyzing the removal of adenine opposite 8-oxo-7,8-dihydroguanine or guanine in duplex DNA. Although the x-ray crystal structure of the catalytic domain of MutY revealed a mechanism for catalysis of the glycosyl bond, it appeared that several opportunistically positioned lysine side chains could participate in a secondary beta-elimination reaction. In this investigation, it is established via site-directed mutagenesis and the determination of a 1.35-A structure of MutY in complex with adenine that the abasic site (apurinic/apyrimidinic) lyase activity is alternatively regulated by two lysines, Lys142 and Lys20. Analyses of the crystallographic structure also suggest a role for Glu161 in the apurinic/apyrimidinic lyase chemistry. The beta-elimination reaction is structurally and chemically uncoupled from the initial glycosyl bond scission, indicating that this reaction occurs as a consequence of active site plasticity and slow dissociation of the product complex. MutY with either the K142A or K20A mutation still catalyzes beta and beta-delta elimination reactions, and both mutants can be trapped as covalent enzyme-DNA intermediates by chemical reduction. The trapping was observed to occur both pre- and post-phosphodiester bond scission, establishing that both of these intermediates have significant half-lives. Thus, the final spectrum of DNA products generated reflects the outcome of a delicate balance of closely related equilibrium constants.
Source: Journal of Biological Chemistry
Language: English
Topic: DNA Repair Mechanisms
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $3,430
OpenAlex ID: W2087791144