The proofreading pathway of bacteriophage T4 DNA polymerase

Linda J. Reha-Krantz, Leah A. Marquez, Elena Elisseeva, Rosanna P. Baker, Linda B. Bloom, H. Brian Dunford, Myron F. Goodman

Research output: Contribution to journalArticlepeer-review

37 Scopus citations


The base analog, 2-aminopurine (2AP), was used as a fluorescent reporter of the biochemical steps in the proofreading pathway catalyzed by bacteriophage T4 DNA polymerase. 'Mutator' DNA polymerases that are defective in different steps in the exonucleolytic proofreading pathway were studied so that transient changes in fluorescence intensity could be equated with specific reaction steps. The G255S- and D131N-DNA polymerases can hydrolyze DNA, the final step in the proofreading pathway, but the mutator phenotype indicates a defect in one or more steps that prepare the primer-terminus for the cleavage reaction. The hydrolysis-defective D112A/E114A-DNA polymerase was also examined. Fluorescent enzyme-DNA complexes were preformed in the absence of Mg2+, and then rapid mixing, stopped-flow techniques were used to determine the fate of the fluorescent complexes upon the addition of Mg2+. Comparisons of fluorescence intensity changes between the wild type and mutant DNA polymerases were used to model the exonucleolytic proofreading pathway. These studies are consistent with a proofreading pathway in which the protein loop structure that contains residue Gly255 functions in strand separation and transfer of the primer strand from the polymerase active center to form a preexonuclease complex. Residue Asp131 acts at a later step in formation of the preexonuclease complex.

Original languageEnglish (US)
Pages (from-to)22969-22976
Number of pages8
JournalJournal of Biological Chemistry
Issue number36
StatePublished - Sep 4 1998
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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