Figure 6.

Effect of calcium on exonuclease and DNA polymerase activities by various families of DNA Pols. The characteristics of families A, B, D, X and Y DNA Pols distributed across the three kingdom of life are summarized. The primer-template used for primer extension experiments and 3′-exonuclease primer degradation, in panels A–C and B–D, consists of a Cy5-labeled 17-mer primer annealed to a DNA template of 87-nt in length. (A–C) Extension of the 17/87 primer-template by DNA Pols at fixed Mg²⁺ or Ca²⁺ concentrations (5 mM). The extension (%) for selected lanes is shown under the gel. Reference oligodeoxynucleotides of 17 and 87 bases are indicated by the arrows. (B–D) Proofreading exonucleolysis of 17/87 primer-template at 5 mM Mg²⁺ or Ca²⁺ concentrations. The degradation (%) for selected lanes is shown under the gel. Reference oligodeoxynucleotides of 17 and 8 bases are indicated by the arrows. Black lines separate lanes which were not adjacent in the original gel.