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Infect. Immun., Jun 1997, 2183-2189, Vol 65, No. 6
I Golovliov, M Ericsson, G Sandstrom, A Tarnvik and A Sjostedt
The adaptation of facultative intracellular bacteria to host macrophages
involves regulation of the synthesis of bacterial proteins. We analyzed the
protein synthesis of Francisella tularensis LVS growing intracellularly in
the macrophage-like murine cell line J774 and extracellularly in culture
medium. After pulse-labeling with [35S] methionine and separation by one-
and two-dimensional polyacrylamide gel electrophoresis, induction of a few
proteins during intracellular growth was demonstrated. One of them, a
23-kDa protein, was prominently induced in the macrophages and also when
extracellularly growing F. tularensis was exposed to hydrogen peroxide.
After isolation of the 23- kDa protein from a preparative two-dimensional
gel, a 22-amino-acid N- terminal peptide and two peptides obtained by
trypsin digestion were sequenced. Based on the sequences, degenerate
oligonucleotides were constructed for use as primers in a PCR.
Hybridization of amplified DNA to XbaI-digested LVS DNA identified the gene
of the 23-kDa protein in a 1.3-kb DNA fragment. Nucleotide sequence
analysis revealed an open reading frame encoding a putative protein of a
calculated molecular mass of 22.2 kDa. The open reading frame was preceded
by a sequence typical of ribosome-binding sites in Escherichia coli. The
amplified gene was successfully expressed by the pTrc99A vector in E. coli
under control of the trc promoter. The gene product showed the same
mobility and immunoreactivity as the 23-kDa protein of F. tularensis. The
deduced amino acid sequence showed no significant homology with protein
sequences in current data banks. Thus, intracellular growth of F.
tularensis in macrophages was associated with prominent upregulation of a
novel 23-kDa protein.
Copyright © 1997, American Society for Microbiology
Identification of proteins of Francisella tularensis induced during growth in macrophages and cloning of the gene encoding a prominently induced 23-kilodalton protein
Department of Microbiology, National Defence Research Establishment, Umea, Sweden.
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