The nucleoid-associated DNA-binding protein H-NS is required for the efficient adaptation of Escherichia coli K-12 to a cold environment |
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Authors: | Petra Dersch Susanne Kneip and Erhard Bremer |
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Institution: | (1) Max-Planck-Institut für Terrestrische Mikrobiologie, Karl-von-Frisch Str., D-35043 Marburg, Germany |
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Abstract: | The hns gene is a member of the cold-shock regulon, indicating that the nucleoid-associated, DNA-binding protein H-NS plays an important role in the adaptation of Escherichia coli to low temperatures. We show here that the ability to cope efficiently with a cold environment (12°C and 25°C) is strongly impaired in E. coli strains carrying hns mutations. Growth inhibition is much more pronounced in strains carrying the hns-206 allele (an ampicillin resistance cassette inserted after codon 37) than in those carrying the hns-205 mutation (a Tn10 insertion located in codon 93). A protein fragment (H-NS*) is synthesized in strains carrying the hns-205::Tn10 mutation, suggesting that this truncated polypeptide is partially functional in the cold adaptation process. Analysis of the growth properties of strains harbouring four different low-copy-number plasmid-encoded hns genes that result in the production of C-terminally truncated H-NS proteins supports this proposal. H-NS* proteins composed of 133, 117 or 94 amino-terminal amino acids partially complemented the severe cold-sensitive growth phenotype of the hns-206 mutant. In contrast, synthesis of a truncated H-NS protein with only 75 amino-terminal amino acids was insufficient to restore growth at low temperature. |
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Keywords: | Adaptation to low temperature DNA-binding protein H-NS hns mutants Truncated proteins |
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