Figure 3.

Dye competition assay using purified LanP (Mfla_0908).A, control assays performed in the absence of LanP or in the presence of bovine serum albumin (BSA) (2 μM) using different lanthanides for titration. The absorbance increase at 660 nm indicates the binding of Ln³⁺ to arsenazo III (10 μM). The equivalents Ln³⁺ shown in the x-axis are based on the 2 μM LanP used in B. The shaded areas represent the standard deviation of three independent assays. B, competition assay between 2 μM LanP and 10 μM arsenazo III. The delay in absorbance increase compared with the control (A) is due to the binding of Ln³⁺ by LanP. The number of binding sites was estimated based on the molar equivalent Ln³⁺ required to reach 15% of the maximum absorbance, indicating saturation of the binding sites on LanP. The values are reported as mean ± standard deviation (n = 3). C, competition assay similar as in B, but La³⁺ was titrated into a solution containing in addition 20 mM CaCl₂.