title: T7 DNA polymerase is not a zinc-metalloenzyme and the polymerase and exonuclease activities are inhibited by zinc ions.
abstract: Phage T7 DNA polymerase purified to homogeneity by an antithioredoxin immunoadsorbent technique was resolved into its active subunits the gene 5 protein and Escherichia coli thioredoxin by a novel technique involving chromatography on Sephadex G-50 at pH 11.5. Analysis of the metal content of the holoenzyme by atomic absorption spectroscopy showed that it did not contain stoichiometric amounts of zinc. Determination of polymerase and exonuclease activities of the holoenzyme and the gene 5 protein in assay mixtures containing enzyme concentrations in excess of the Zn2+ concentration showed full activity. Addition of Zn2+ resulted in no stimulation and the activities were completely inhibited by 0.1 mM Zn2+. These results demonstrate that the essential T7 DNA polymerase is not a zinc-metalloenzyme and suggest that DNA polymerases show no functional requirement for Zn2+.
mesh_terms: D002712:Chlorides; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D004492:Edetic Acid / Q000494:pharmacology; D004926:Escherichia coli / Q000201:enzymology*; D007700:Kinetics; D008667:Metalloproteins / Q000032:analysis; D019384:Nucleic Acid Synthesis Inhibitors; D013054:Spectrophotometry, Atomic; D013604:T-Phages / Q000201:enzymology*; D014764:Viral Proteins / Q000032:analysis; D015032:Zinc / Q000032:analysis / Q000494:pharmacology*; D017967:Zinc Compounds
chemical_list: D002712:Chlorides; D008667:Metalloproteins; D019384:Nucleic Acid Synthesis Inhibitors; D014764:Viral Proteins; D017967:Zinc Compounds; C016837:zinc chloride; D004492:Edetic Acid; D004259:DNA-Directed DNA Polymerase; D015032:Zinc