Figure 3.

Sso DNA primase has 3′-terminal nucleotidyl-transferase activity. The 3′-terminal nucleotidyl-transferase activity of Sso DNA primase was assayed on the indicated 5′-terminally labelled synthetic substrates (reaction volume: 20 μl), as described in Materials and Methods. Reaction products (6 μl of each reaction mixture) were analyzed by electrophoresis using 20% or 6% polyacrylamide/urea gels for the 25 or 56mer oligonucleotides, respectively. The radioactivity was detected by using a phosphorimager. Lanes 2–5 of each gel were loaded with reaction mixtures containing only the indicated rNTP in addition to the DNA template and the enzyme, whereas lane 1 contains a control reaction without enzyme.