Figure 2.

Metal binding titration data and fits for HQuin1 (3 – 5 μM) in the presence of EGTA (25-100 μM) as a competing ligand and various concentrations of (a) Co²⁺, (b) Ni²⁺, (c) Cu²⁺, (d) Zn²⁺ as monitored by UV-vis spectroscopy. Regression analysis was performed using both a simple 1:1 (solid line) metal:protein binding model and a combined 1:1 and 1:2 (dotted line) model, the latter of which accounts for metal-induced protein dimerization. A minimum of two titrations under identical conditions were performed for each metal and their results averaged. Metal dissociation constants (K_d^metal) determined through these titrations are listed in Tables 1, S2.1 and S2.2. DynaFit expressions used for data fitting are given in the Supporting Information.