DNA polymerase gamma from Xenopus laevis. II. A 3'----5' exonuclease is tightly associated with the DNA polymerase activity

• Published in: The Journal of biological chemistry Vol. 264; no. 36; pp. 21498 - 21503
• Main Authors: INSDORF, N. F, BOGENHAGEN, D. F
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Biochemistry and Molecular Biology 25.12.1989
• Subjects: Analytical, structural and metabolic biochemistry; Animals; Base Sequence; Biological and medical sciences; DNA Polymerase III - isolation & purification; DNA Polymerase III - metabolism; DNA-Directed DNA Polymerase - metabolism; Enzymes and enzyme inhibitors; Exodeoxyribonuclease V; Exodeoxyribonucleases - isolation & purification; Exodeoxyribonucleases - metabolism; Female; Fundamental and applied biological sciences. Psychology; Kinetics; Molecular Sequence Data; Molecular Weight; Oligodeoxyribonucleotides; Oocytes - enzymology; Protein Denaturation; Substrate Specificity; Transferases; Xenopus laevis; Spleen exonuclease; Vertebrata; Enzymatic activity; Radiolabelling; Enzyme; Xenopus laevis; Amphibia; Molecular association; Gel filtration; Salientia; DNA polymerase γ
• ISSN: 0021-9258; 1083-351X

Xenopus laevis DNA polymerase gamma co-purifies with a tightly associated 3'---5' exonuclease. The purified enzyme lacks 5'---3' exonuclease and endonuclease activity. The ratio of the 3'---5' exonuclease activity to DNA polymerase gamma activity remains constant over the final three chromatographic procedures. In addition, these activities co-sediment under partially denaturing conditions in the presence of ethylene glycol. The associated 3'---5' exonuclease activity removes a terminally mismatched nucleotide more rapidly than a correctly base-paired 3'-terminal residue, as expected if this exonuclease has a proofreading function. The 3'---5' exonuclease has the ability to release a terminal phosphorothioated nucleotide, a property shared with T4 DNA polymerase, but not with Escherichia coli DNA polymerase I.