Applied and Environmental Microbiology, May 1999, p. 2112-2115, Vol. 65, No. 5
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.

Department of Food Science and
Technology2 and the School of Biological
Sciences,1 University of Nebraska
Lincoln,
Lincoln, Nebraska 68583-0919
Received 4 December 1998/Accepted 10 March 1999
The regulatory role of HPr, a protein of the phosphotransferase system (PTS), was investigated in Listeria monocytogenes. By constructing mutations in the conserved histidine 15 and serine 46 residues of HPr, we were able to examine how HPr regulates PTS activity. The results indicated that histidine 15 was phosphorylated in a phosphoenolpyruvate (PEP)-dependent manner and was essential for PTS activity. Serine 46 was phosphorylated in an ATP-dependent manner by a membrane-associated kinase. ATP-dependent phosphorylation of serine 46 was significantly enhanced in the presence of fructose 1,6-diphosphate and resulted in a reduction of PTS activity. The presence of a charge at position 15 did not inhibit ATP-dependent phosphorylation of serine 46, a finding unique to gram-positive PEP-dependent PTSs studied to this point. Finally, HPr phosphorylated at serine 46 does not appear to possess self-phosphatase activity, suggesting a specific phosphatase protein may be essential for the recycling of HPr to its active form.
Paper no. 12384 of the Journal Series of the Nebraska Agricultural
Experiment Station, Lincoln.
Present address: Mathematics and Sciences Division, Wayne State
College, Wayne, NE 68787.
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