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- Title
Cloning and molecular characterization of a <em>Legionella pneumophila</em> gene induced by intracellular infection and by various <em>in vitro</em> stress conditions.
- Authors
Kwaik, Yousef Abu; Engleberg, N. Cary
- Abstract
The synthesis of a global stress protein (GspA) of <em>Legionella pneumophila</em> is induced in the intracellular environment of the phagocytic cell and by various <em>in vitro</em> stress stimuli. We used techniques of reverse genetics to isolate the <em>gspA</em> gene from a genomic library of <em>L. pneumophila</em>. Sequence analysis of approximately 1700 bp of a representative clone (pBSP1) showed the presence of two open reading frames (ORFs). ORF1 encoded for a polypeptide with an inferred molecular mass of 19 kDa and an isoelectric point of 6.1. These predictions correlated with the migration of the GspA protein on two-dimensional SDS-polyacrylamide gels. The predicted amino acid sequence of the GspA protein was identical to 22/23 residues of the <em>N</em>-terminal amino acid sequence derived by Edman degradation of the purified protein. The GspA protein was 41.3% and 36.5% identical to the 16 kDa lbpA and lbpB heat-shock proteins, respectively, of <em>Escherichia coli</em>. Primer extension from mRNA isolated from <em>L. pneumophila</em> showed that transcription of the <em>gspA</em> gene was controlled by two overlapping promoters. One of the promoters was a σ70 promoter, while the other was a heat-shock promoter and was regulated by the σ32 transcription factor in <em>E. coli</em>. Northern biot analysis showed that the level of <em>gspA</em> mRNA was elevated 3.4-, 5.0-, and 6.7-fold after exposure of <em>L. pneumophila</em> to heat shock, oxidative stress and osmotic shock, respectively. The <em>gspA</em> gene was conserved among 13 serogroups of <em>L. pneumophila</em>. Our data showed that the <em>gspA</em> gene of <em>L. pneumophila</em>, which is induced by intracellular infection and by various stress stimuli, is controlled transcriptionally by two overlapping and separately regulated promoters.
- Subjects
HEAT shock proteins; PROTEINS; LEGIONELLA pneumophila; LEGIONELLA; GENES; GENOMES
- Publication
Molecular Microbiology, 1994, Vol 13, Issue 2, p243
- ISSN
0950-382X
- Publication type
Article
- DOI
10.1111/j.1365-2958.1994.tb00419.x