The role of enzyme I in the unmasking of an essential thiol of the membrane-bound enzyme II of the phosphoenolpyruvate-glucose phosphotransferase system of Escherichia coli

Abstract

The membrane-bound component of the phosphotransferase system of Escherichia coli, responsible for the phosphorylative uptake of methyl-alpha-D-glucoside has an essential thiol group which becomes available to inactivation by thiol reagents in the presence of the phosphate-accepting sugar or when phosphoenolpyruvate synthesis is inhibited. The form resistant to the thiol reagent requires not only the absence of sugar and an intact phosphoenolpyruvate generating system, but also an intact system generating phosphorylated Hpr which is impaired by heating of a thermosensitive enzyme I mutant.