Properties of phosphorylated protein intermediates of the bacterial phosphoenolpyruvate:sugar phosphotransferase system

Abstract

The phosphohydrolysis properties of the following phosphoprotein intermediates of the bacterial phosphoenolpyruvate:sugar phosphotransferase system (PTS) were investigated: enzyme I, HPr, and the IIAGlc domain of the glucose enzyme II of Bacillus subtilis; and IIAGlc (fast and slow forms) of Escherichia coli. The phosphohydrolysis properties were also studied for the site-directed mutant H68A of B. subtilis IIAGlc. Several conclusions were reached. (i) The phosphohydrolysis properties of the homologous phosphoprotein intermediates of B. subtilis and E. coli are similar. (ii) These properties deviate from those of isolated Nδ1- and Nε2-phosphohistidine indicating the participation of neighbouring residues at the active sites of these proteins. (iii) The rates of phosphohydrolysis of the H68A mutant of B. subtilis IIAGlc were reduced compared with the wild-type protein, suggesting that both His-83 and His-68 are present at the active site of wild-type IIAGlc. (iv) The removal of seven N-terminal residues of E. coli IIAGlc reduced the rates of phosphohydrolysis between pH 5 and 8.Key words: phosphoenolpyruvate:sugar phosphotransferase system, phosphoproteins, phosphohistidine, phosphorylation, sugar transport.