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J. Bacteriol., 08 1995, 4238-4244, Vol 177, No. 15
M Zuber, TA Hoover and DL Court
A 1.2-kb EcoRI genomic DNA fragment of Coxiella burnetti, when cloned onto
a multicopy plasmid, was found to induce capsule synthesis (mucoidy) in
Escherichia coli. Nucleotide sequence analysis revealed the presence of an
open reading frame that could encode a protein of 270 amino acids.
Insertion of a tet cassette into a unique NruI restriction site resulted in
the loss of induction of mucoidy. Because of its ability to induce mucoidy,
we designated this gene mucZ. Computer search for homologies to mucZ
revealed 42% identity to an open reading frame located at 1 min of the E.
coli chromosome. Interestingly, the C-terminal amino acid residues of MucZ
share significant homology with the J domain of the DnaJ protein and its
homologs, suggesting potential interactions between MucZ and components of
the DnaK-chaperone machinery. Results presented in this paper suggest that
E. coli requires DnaK-chaperone machinery for Lon-RcsA- mediated induction
of capsule synthesis, as noticed first by S. Gottesman (personal
communication). The induction caused by MucZ is independent of Lon-RcsA and
is mediated through the two-component regulators RcsC and RcsB. DnaK and
GrpE but not DnaJ are also required for the RcsB-mediated MucZ induction,
and we propose that MucZ is a DnaJ-like chaperone protein that might be
required for the formation of an active RcsA-RcsB complex and for the
RcsC-dependent phosphorylation of RcsB. Discussions are presented that
suggest three different roles for alternative forms of the DnaK-chaperone
machinery in capsule production.
Copyright © 1995, American Society for Microbiology
Analysis of a Coxiella burnetti gene product that activates capsule synthesis in Escherichia coli: requirement for the heat shock chaperone DnaK and the two-component regulator RcsC
Toxinology Division, U.S. Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, Maryland 21702-5011, USA.
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