What question did this study set out to answer?

To resolve the catalytic sequence and timing of sugar ring opening versus covalent intermediate formation during DNA cleavage by glycosylase/AP lyases.

December 20, 2000Biochemistry

The Reaction Mechanism of DNA Glycosylase/AP Lyases at Abasic Sites

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Authors

AMAmanda K. McCulloughOregon Health & Science University ASAna M. SánchezMemorial Sloan Kettering Cancer Center MDM.L. DodsonIntermountain Healthcare

Discussion

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Implication

Biochemical analysis uncovers cleavage initiation at closed abasic sites in DNA, indicating nucleophilic displacement precedes ring opening during base excision repair.

Key Points

To resolve the catalytic sequence and timing of sugar ring opening versus covalent intermediate formation during DNA cleavage by glycosylase/AP lyases.
Measured and compared the combined rates of sugar ring opening and aldehyde reduction against the rate of T4-pyrimidine dimer glycosylase (T4-pdg)-DNA intermediate formation.
Assayed T4-pdg cleavage activity and stereospecificity on anomer variants of a ring-closed methyl-deoxyribofuranose abasic site analogue.
Examined the sodium borohydride concentration dependence of covalent imine intermediate formation to identify the rate-limiting reaction step.
T4-pdg-DNA intermediate formation occurred significantly faster than the combined rate of sugar ring opening and reduction, confirming that reaction initiation does not require prior ring opening.
T4-pdg cleaved the ring-closed methyl-deoxyribofuranose analogue at a markedly reduced rate with strong stereoselective preference for the beta-anomer via backside displacement from the alpha-face.
Sodium borohydride concentration dependence during intermediate trapping demonstrated that reduction of the covalent imine intermediate is the rate-limiting step.

Cite This Study

McCullough et al. (2000) studied this question.

synapsesocial.com/papers/6aa047f98a599f85a3af7f75 https://doi.org/10.1021/bi002404+

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Implication

Biochemical analysis uncovers cleavage initiation at closed abasic sites in DNA, indicating nucleophilic displacement precedes ring opening during base excision repair.

The Reaction Mechanism of DNA Glycosylase/AP Lyases at Abasic Sites

Discussion

Member takes

Implication

Key Points

Cite This Study

The Reaction Mechanism of DNA Glycosylase/AP Lyases at Abasic Sites

Discussion

Member takes

Implication

Key Points

Cite This Study

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