Sie befinden Sich nicht im Netzwerk der Universität Paderborn. Der Zugriff auf elektronische Ressourcen ist gegebenenfalls nur via VPN oder Shibboleth (DFN-AAI) möglich. mehr Informationen...
Transition-State Analysis of the DNA Repair Enzyme MutY
Ist Teil von
Journal of the American Chemical Society, 2008-04, Vol.130 (17), p.5789-5797
Ort / Verlag
United States: American Chemical Society
Erscheinungsjahr
2008
Quelle
MEDLINE
Beschreibungen/Notizen
The transition state (TS) structure of MutY-catalyzed DNA hydrolysis was solved using multiple kinetic isotope effect (KIE) measurements. MutY is a base excision repair enzyme which cleaves adenine from 8-oxo-G:A mismatches in vivo, and also from G:A mismatches in vitro. TS analysis of G:A-DNA hydrolysis revealed a stepwise SN1 (DN*AN ‡) mechanism proceeding through a highly reactive oxacarbenium ion intermediate which would have a lifetime in solution of <10−10 s. C−N bond cleavage is reversible; the N-glycoside bond breaks and reforms repeatedly before irreversible water attack on the oxacarbenium ion. KIEs demonstrated that MutY uses general acid catalysis by protonating N7. It enforces a 3′-exo sugar ring conformation and other sugar ring distortions to stabilize the oxacarbenium ion. Combining the experimental TS structure with the previously reported crystal structure of an abortive Michaelis complex elucidates the step-by-step catalytic sequence.