Fig. 4.

Fe²⁺ consistently supports 50 to 80% of the translational activity as Mg²⁺ when the translation experiments are run for 15 min to 120 min. The activity of the translation product (DHFR, which catalyzes the oxidation of NADPH, with a maximum absorbance at 340 nm) was used as a proxy for protein production. All translation reactions contained 2.5 mM background Mg²⁺, to which 7 mM additional Mg²⁺ or Fe²⁺ were added, totaling 9.5 mM divalent cation. The error bars for triplicate experiments (n = 3) are plotted as the SEM.