INFLUENCE OF PHOSPHOENOLPYRUVATE AND MAGNESIUM-IONS ON THE QUATERNARYSTRUCTURE OF ENZYME-I OF THE PHOSPHOTRANSFERASE SYSTEM FROM GRAM-POSITIVE BACTERIA

Solution X-ray scattering patterns of enzyme I of the phosphotransfera se system from Staphylococcus carnosus indicate an increase in radius of gyration and molecular mass in the presence of Mg2+ or both Mg2+ an d phosphoenolpyruvate, indicating a partial dimerization of enzyme I. Mg2+ ions are essential for both the dimerization and the activation, whereas the substrate phosphoenolpyruvate shifts the monomer-dimer equ ilibrium to the enzymatically active dimer by decreasing the dissociat ion rate of the phosphorylated dimer.