Figure 7.

Ferroxidase activity of EncFtn WT and variants is inhibited by zinc. A, comparisons between data shown in Fig. 6A, collected in the absence of competing metals, are here plotted with curves from ferroxidase assays of EncFtn WT and variants carried out using [protein] = 10 µm and [Fe(II)] = 50 µm in the presence of [Zn(II)] = 34 µm. The zinc concentration corresponds to a response inhibited by 50% for EncFtn-Strep under the same experimental conditions (14). EncFtn-WT is represented by a dark green line, EncFtn-E34A by a purple line, EncFtn-E31A by a pale blue line, and EncFtn-W38A by a red line. As a control, a mix of Fe(II) and Zn(II) salts (gray dotted line) was assayed in the absence of the enzyme. B, end-point data presented in (A) were plotted as columns to compare inhibition by zinc. Percentage of inhibition is shown above in corresponding columns. Color-coding is consistent with (A).