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J Bacteriol, February 1998, p. 732-736, Vol. 180, No. 3
DNA Technologies Group, Biotechnology
Division, Chemical Science and Technology Laboratory, National
Institute of Standards and Technology, Gaithersburg, Maryland 20899
Received 24 March 1997/Accepted 22 October 1997
It is demonstrated here that in Escherichia coli, the
phosphorylated form of the glucose-specific phosphocarrier protein
IIAGlc of the phosphoenolpyruvate:sugar phosphotransferase
system is an activator of adenylyl cyclase and that unphosphorylated
IIAGlc has no effect on the basal activity of adenylyl
cyclase. To elucidate the specific role of IIAGlc
phosphorylation in the regulation of adenylyl cyclase activity, both
the phosphorylatable histidine (H90) and the interactive histidine
(H75) of IIAGlc were mutated by site-directed mutagenesis
to glutamine and glutamate. Wild-type IIAGlc and the H75Q
mutant, in which the histidine in position 75 has been replaced by
glutamine, were phosphorylated by the phosphohistidine-containing phosphocarrier protein (HPr~P) and were equally potent activators of
adenylyl cyclase. Neither the H90Q nor the H90E mutant of
IIAGlc was phosphorylated by HPr~P, and both failed to
activate adenylyl cyclase. Furthermore, replacement of H75 by glutamate
inhibited the appearance of a steady-state level of phosphorylation of
H90 of this mutant protein by HPr~P, yet the H75E mutant of
IIAGlc was a partial activator of adenylyl cyclase. The
H75E H90A double mutant, which cannot be phosphorylated, did not
activate adenylyl cyclase. This suggests that the H75E mutant was
transiently phosphorylated by HPr~P but the steady-state level of the
phosphorylated form of the mutant protein was decreased due to the
repulsive forces of the negatively charged glutamate at position 75 in
the catalytic pocket. These results are discussed in the context of the
proximity of H75 and H90 in the IIAGlc structure and the
disposition of the negative charge in the modeled glutamate mutants.
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Modulation of Escherichia coli Adenylyl Cyclase
Activity by Catalytic-Site Mutants of Protein IIAGlc of
the Phosphoenolpyruvate:Sugar Phosphotransferase System
*
Corresponding author. Mailing address: DNA
Technologies Group, Biotechnology Division, Chemical Science and
Technology Laboratory, Building 222, Room A359, National Institute of
Standards and Technology, Gaithersburg, MD 20899-0001. Phone: (301)
975-4871. Fax: (301) 330-3447. E-mail:
prasad{at}enh.nist.gov.
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