Differential effect of MgCl2 concentration on capping activities. FCE and VCE exhibit the highest capping activity in 0.5–2 mM MgCl2, but individual activities of the two enzymes are differentially affected outside of the optimal MgCl2 concentration range. At 0.1 mM MgCl2, the TPase activity of FCE is impeded whereas in VCE the GTase activity was affected. For FCE, the GTase activity was negatively impacted at 5 mM MgCl2 with TPase starting to be affected at 10 mM MgCl2. For VCE, the GTase activity started to be affected at 5 mM MgCl2 as indicated by pp-RNA accumulation. However, the TPase activity of VCE was not affected up to 20 mM MgCl2 due to the lack of ppp− accumulation. In each experiment, 5 nM of enzymes and 0.5 mM of RNA substrate were used. Data points are the average value of triplicated experiments. Error bars represent standard deviations.
