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Microbiology. 2000 Jan;146 ( Pt 1):77-88. doi: 10.1099/00221287-146-1-77.

Chaperone-like activities of the CsaA protein of Bacillus subtilis.

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Institute for Molecular Biology, Jena University, Winzerlaer Strasse 10, 07745 Jena, Germany1.
Department of Genetics, Center for Biological Sciences, Kerklaan 30, 9751 NN Haren, The Netherlands2.
Department of Pharmaceutical Biology, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands3.


The growth and protein export defects of Escherichia coli secA51(Ts) strains can be suppressed by the CsaA protein of Bacillus subtilis. The present studies indicate that this effect can be attributed to chaperone-like activities of CsaA. First, CsaA stimulated protein export in secB, groES and dnaJ mutant strains of E. coli. Second, CsaA suppressed the growth defects of dnaK, dnaJ and grpE mutants of E. coli. Third, and most importantly, CsaA exhibited chaperone-like properties by stimulating the reactivation of heat-denatured firefly luciferase in groEL, groES, dnaK and grpE mutant strains of E. coli, and by preventing the aggregation of heat-denatured luciferase in vitro. Thus, it seems that CsaA suppresses the growth and secretion defects of E. coli secA(Ts) strains either by improving the translocation competence of exported pre-proteins, thereby making them better substrates for mutant SecA proteins, or by stimulating the translocation activity of mutant SecA proteins.

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