FIGURE 3.
Primase robustly extends RNA primers only in the presence of ribonucleotides. The poly-rA15 primer (enzyme to primer/template ratio = 1:1.5) was extended by heterodimeric primase (p49·p58) in the presence of rATP, dATP, or both. Lane 1, reaction without nucleotides; lanes 2–4, reaction with 0.2 mm ATP for 0.5, 2.0, and 5.0 min, respectively; lanes 5–7, reaction with 0.4 mm dATP for 0.5, 2.0, and 5.0 min, respectively; lanes 8–10, reaction with 0.2 mm ATP plus 0.4 mm dATP for 0.5, 2.0, and 5.0 min, respectively. nt, nucleotides.