Figure 1
From: Analysis of the stoichiometric metal activation of methionine aminopeptidase
Three different scenarios in metal activation of a metalloenzyme. The enzyme is activated by only a single metal per protein (Case 1) or by two metals (Cases 2 and 3). In each of the three cases, vertical positions represent the relative values of protein concentration, and KD and KD2 for the first and second metal sites M1 and M2. (A) Simulated stoichiometric titrations for Case 1. The KD value was set to 0.2 μM with n = 1, and the protein concentration was set at 20, 2 or 0.2 μM (yielding 100:1, 10:1 or 1:1 [protein]/KD ratio). (B) Simulated stoichiometric titrations for Case 2. Both the KD and KD2 values were fixed at 0.2 μM, with the total protein concentration of 20, 2 or 0.2 μM (resulting in 100:1, 10:1 or 1:1 [protein]/KD ratio) and n = 2. (C) Simulated stoichiometric titrations for Case 3. The KD value for the tight metal site M1 was fixed at 0.2 μM, and the KD2 value for the weaker site was set at 20 μM, with the total protein concentration of 2000, 200 or 20 μM, giving a 100:1, 10:1 or 1:1 [protein]/KD2 ratio.