DNA polymerases from Chlamydomonas reinhardii. Purification and properties.
Three DNA polymerase activities, A, B and C, were identified in extracts of exponentially growing synchronous cultures of Chlamydomonas reinhardii, and DNA polymerases A and B were characterized in detail. Both enzymes have the same binding affinity for DEAE-cellulose at pH 7.8, but can be distinguished from each other by their behaviour on phosphocellulose and DNA-agarose. 'Activated' calf thymus DNA was used as template, and the pH, K+ and bivalent-cation optima were measured. DNA polymerase A sediments at 5.3 S in glycerol gradients, with an apparent mol.wt. of 90000-100000. Polymerase B sediments between 8S and 10S in 100mM-KCl, the predominant species having an apparent mol.wt. of 200000. In 200mM-KCl, polymerase B dissociates to a single species, which sediments at 5.8S. A 3S species was found in aged preparations of both enzymes. The activity of polymerase B from cells harvested during nuclear DNA synthesis is twice that found in Chlamydomonas at other times during the cell cycle.
DNA polymerases from Chlamydomonas reinhardii. Purification and properties. Three DNA polymerase activities, A, B and C, were identified in extracts of exponentially growing synchronous cultures of Chlamydomonas reinhardii, and DNA polymerases A and B were characterized in detail. Both enzymes have the same binding affinity for DEAE-cellulose at pH 7.8, but can be distinguished from each other by their behaviour on phosphocellulose and DNA-agarose. 'Activated' calf thymus DNA was used as template, and the pH, K+ and bivalent-cation optima were measured. DNA polymerase A sediments at 5.3 S in glycerol gradients, with an apparent mol.wt. of 90000-100000. Polymerase B sediments between 8S and 10S in 100mM-KCl, the predominant species having an apparent mol.wt. of 200000. In 200mM-KCl, polymerase B dissociates to a single species, which sediments at 5.8S. A 3S species was found in aged preparations of both enzymes. The activity of polymerase B from cells harvested during nuclear DNA synthesis is twice that found in Chlamydomonas at other times during the cell cycle.