Effect of calcium on Tth PAC overproduction in E. coli cells. CaCl2 concentrations up to 50 mM were added to the LB media at the beginning of E. coli cells cultivation. Tth PAC maturation and activity were evaluated. (A) Western blot against α- and β-Tth PAC subunits. Lane 1–5, increasing calcium concentrations; lane 6 (C), Tth PAC matured in Tth cells. (B) Optical density at 600nm (circles), specific (squares) and volumetric (triangles) activity of Tth PAC.