Figure 3.

Fidelity of Polη during DNA and RNA synthesis in the presence of magnesium or manganese. (A,B) Reactions contained 5-mM Mn²⁺ or Mg²⁺ as indicated, 6-nM Polη, 20-nM (A) DNA/DNA (S1–4) or (B) RNA/DNA (S5–8) primer/template, and (A) 0.1-mM individual dNTPs or (B) 4 mM individual rNTP, as indicated. Reaction times were 1 min except for the 15-min reactions with Mg²⁺ in (B). The templating base in the incoming position is denoted. RNA primer and rNTPs are highlighted in red, and manganese is in blue. The nucleotides representing correct insertions are boxed. (C) Measured k_cat (left) and K_M (right) values of various ribunucleotide incorporations opposite the indicated templating bases. (D) Heat map showing relative catalytic constants of incorporation of incorrect versus correct rNTPs. Log.Rel.kcat = Log10(k_{cat incorrect}/k_{cat correct}), Log.Rel.Km = Log10(K_{M incorrect}/K_{M correct}) and Log.Rel.Effic = Log10 [(k_cat/K_M)_incorrect/(k_cat/K_M)_correct]. Heat map was generated using http://www.heatmapper.ca [40].