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Journal of Bacteriology, February 1999, p. 833-840, Vol. 181, No. 3
Laboratoire de Chimie Structurale des
Macromolécules,1
Station Centrale
de Microscopie Electronique,2
Laboratoire d'Ingénierie des
Anticorps,3 and
Unité de
Régulation de l'Expression
Génétique,4 Institut Pasteur,
75724 Paris Cedex 15, France
Received 3 August 1998/Accepted 17 November 1998
Mono- and polyclonal antibodies directed against UMP kinase from
Escherichia coli were tested with the intact protein or
with fragments obtained by deletion mutagenesis. As detected in
enzyme-linked immunosorbent assay tests, the carboxy-terminal quarter
of UMP kinase is immunodominant. Polyclonal antibodies inhibited the enzyme activity with partial or total loss of allosteric effects exerted by UTP and GTP, respectively. These data indicate that the UTP
and GTP binding sites in UMP kinase are only partially overlapping. One
monoclonal antibody (44-2) recognized a linear epitope in UMP kinase
between residues 171 and 180. A single substitution (D174N) in this
segment of the enzyme abolished its interaction with the monoclonal
antibody (44-2). Polyclonal antisera were used to identify UMP kinase
in the bacterial proteome. The enzyme appears as a single spot on
two-dimensional electrophoresis at a pI of 7.24 and an apparent
molecular mass of 26 kDa. Immunogold labeling of UMP kinase in whole
E. coli cells shows a localization of the protein near the
bacterial membranes. Because the protein does not contain sequences
usually required for compartmentalization, the aggregation properties
of UMP kinase observed in vitro might play a role in this phenomenon.
The specific localization of UMP kinase might also be related to its
putative role in cell division.
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Immunochemical Analysis of UMP Kinase from
Escherichia coli
*
Corresponding author. Mailing address: Laboratoire de
Chimie Structurale des Macromolécules, Institut Pasteur, 28, rue
du Docteur Roux, 75724 Paris Cedex 15, France. Phone: 33 (1) 40 61 37 78. Fax: 33 (1) 45 68 84 05. E-mail: hiroshi{at}pasteur.fr.
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