DNA Polymerases of Tetrahymena pyriformis. I. Characterization of Two N-Ethylmaleimide-Sensitive DNA Polymerases from Exponentially Growing Cells
1982 年 91 巻 3 号 p. 845-853
詳細
1982 年 91 巻 3 号 p. 845-853
Two DNA polymerase activities, polymerases A and B, were separated from the Triton-treated cell homogenate of exponentially growing Tetrahymena pyriformis by phosphocellulose column chromatography. Their properties were as follows. Polymerase A: The molecular weight was about 140, 000, the sedimentation value was about 6.2 S, the optimum Mg2+ concentration was 15mM, the optimum K+ (or Na+) concentration was 20mM, and the optimum pH was 7.4. The enzyme activity was inhibited by cytosine-β-D-arabinofuranoside-5'-triphosphate (araCTP) or aphidicolin, but not by 2'-3'-dideoxythymidine-5'-triphosphate (ddTTP). Polymerase B: The molecular weight was about 70, 000, the sedimentation value was 4.3 S, the optimum Mg2+ concentration was 15mM, the optimum K+ (or Na+) concentration was 150mM, and the optimum pH was 8.4. The enzyme activity was inhibited by ddTTP, but not by araCTP or aphidicolin. Polymerases A and B were both found to be N-ethylmaleimide-sensitive.
These results indicate that at least two N-ethylmaleimide-sensitive DNA polymerases, A and B, are present in exponentially growing Tetrahymena cells. Polymerase A bears many similarities to DNA polymerase α of higher eukaryotes and polymerase B also bears similarities to DNA polymerase β except as regards N-ethylmaleimide sensitivity. Based on the properties of polymerases A and B, the relation of Tetrahymena DNA polymerases reported by several investigators is discussed.
