Interaction between the bacterial nucleoid associated proteins Hha and H-NS involves a conformational change of Hha.
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ABSTRACT:
SUBMITTER: Garcia J
PROVIDER: S-EPMC1183454 | biostudies-other | 2005 Jun
REPOSITORIES: biostudies-other
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Project description:The H-NS protein is a major component of the Escherichia coli nucleoid. Mutations in hns, the gene encoding H-NS, have pleiotropic effects on the cell altering both the expression of a variety of unlinked genes and the inversion rate of the DNA element containing the fimA promoter. We investigated the interaction between H-NS and fimB, the gene encoding the bidirectional recombinase that catalyzes fimA promoter flipping. In beta-galactosidase assays, we found that fimB expression increased approximately fivefold in an hns2-tetR insertion mutant. In gel mobility shift assays with purified H-NS, we have also shown that H-NS bound directly and cooperatively to the fimB promoter region with greater affinity than for any other known H-NS-regulated gene. Furthermore, this high-affinity interaction resulted in a promoter-specific inhibition of fimB transcription. The addition of purified H-NS to an in vitro transcription system yielded a fivefold or greater reduction in fimB-specific mRNA production. However, the marked increase in cellular FimB levels in the absence of H-NS was not the primary cause of the mutant rapid inversion phenotype. These results are discussed in regard to both H-NS as a transcriptional repressor of fimB expression and its role in regulating type 1 pilus promoter inversion.
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