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Journal of Bacteriology, September 1998, p. 4828-4833, Vol. 180, No. 18
Department of Microbiology, New York
University Medical Center, New York, New York
10016,1 and
Department of
Biochemistry, Cambridge Center for Molecular Recognition,
University of Cambridge, Cambridge CB2 1QW, United
Kingdom2
Received 28 January 1998/Accepted 1 June 1998
In Escherichia coli K-12, the accumulation of
arginine is mediated by two distinct periplasmic binding
protein-dependent transport systems, one common to arginine and
ornithine (AO system) and one for lysine, arginine, and
ornithine (LAO system). Each of these systems includes a specific
periplasmic binding protein, the AO-binding protein for the AO
system and the LAO-binding protein for the LAO system. The two
systems include a common inner membrane transport protein
which is able to hydrolyze ATP and also phosphorylate the two
periplasmic binding proteins. Previously, a mutant resistant to the
toxic effects of canavanine, with low levels of transport activities and reduced levels of phosphorylation of the two periplasmic binding proteins, was isolated and characterized (R. T. F. Celis, J. Biol. Chem. 265:1787-1793, 1990). The gene encoding
the transport ATPase enzyme (argK) has been
cloned and sequenced. The gene possesses an open reading frame
with the capacity to encode 268 amino acids (mass of
29.370 Da). The amino acid sequence of the protein includes two short
sequence motifs which constitute a well-defined nucleotide-binding fold
(Walker sequences A and B) present in the ATP-binding
subunits of many transporters. We report here the isolation of
canavanine-sensitive derivatives of the previously characterized
mutant. We describe the properties of these suppressor mutations in
which the transport of arginine, ornithine, and lysine has been
restored. In these mutants, the phosphorylation of the AO-
and LAO-binding proteins remains at a low level. This information
indicates that whereas hydrolysis of ATP by the transport ATPase
is an obligatory requirement for the accumulation of these amino acids
in E. coli K-12, the phosphorylation of the periplasmic
binding protein is not related to the function of the transport system.
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Phosphorylation of the Periplasmic Binding Protein in Two
Transport Systems for Arginine Incorporation in Escherichia
coli K-12 Is Unrelated to the Function of the Transport
System
and
*
Corresponding author. Mailing address: Department of
Microbiology, New York University Medical Center, New York, NY 10016. Phone: (212) 263-5115. Fax: (212) 263-8276. E-mail:
CelisR01{at}mcrcr.med.nyu.edu.
Present address: Department of Biochemical Engineering
and Biotechnology, Indian Institute of Technology Delhi,
New Delhi 110016, India.
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