Coupling of proteolysis to ATP hydrolysis upon escherichia coli lon protease functioning. I. kinetic aspects of ATP hydrolysis

摘要

Some aspects of the ATPase function of the Escherichia coli Lon protease were studied around the optimum pH value. It was revealed that, in the absence of the protein substrate, the maximum ATPase activity of the enzyme is observed at an equimolar ratio of ATP and Mg~2+ ions in the area of their millimolar concentrations. Free components of th substrate complex (ATP-Mg)~2- inhibit the enzyme ATPase activity.It is hypothesized that the effector activity of free Mg~2+ ions is caused by the formation of the "ATP-Mg-form" of the ATPase centers. It was shown that the activation of ATP hydrolysis in the presence of the protein substrate is accompanied by an increase in the affinity of the (ATP-Mg)~2- complex to the enzyme,by the elimination of the inhibiting action of free Mg~2+ ions without altering the efficiency of catalysis of catalysis of ATP hydrolysis (based on the k_eat value), and by a change in the type of inhibition of ATP hydrolysis by the (ADP-Mg)~- complex (without changing the K_i value). Interaction of the Lon protease protein substrate with the enzyme area located outside the peptide hydrolase center was demonstrated by a direct experiment.