Abstract
The production of type 1 fimbriae in Salmonella enterica serovar Typhimurium is controlled, in part, by three proteins, FimZ, FimY, and FimW. Amino acid sequence analysis indicates that FimZ belongs to the family of bacterial response regulators of two-component systems. In these studies, we have demonstrated that introducing a mutation mimicking phosphorylation of FimZ is necessary for activation of its target gene, fimA. In addition, the interaction of FimZ with FimW, a repressor of fimA expression, occurs only when FimZ is phosphorylated. Consequently, the negative regulatory effect of FimW is most likely due to downmodulation of the active FimZ protein. FimY does not appear to function as a response regulator, and its activity can be lost by mimicking the phosphorylation of FimY. Overproduction of FimY cannot alleviate the nonfimbriate phenotype in a FimZ mutant, whereas high levels of FimZ can overcome the nonfimbriate phenotype of a FimY mutant. It appears that FimY acts upstream of FimZ to activate fimA expression.
Highlights
The production of type 1 fimbriae in Salmonella enterica serovar Typhimurium is controlled, in part, by three proteins, FimZ, FimY, and FimW
In Salmonella enterica serovar Typhimurium fim gene expression, there are no site-specific recombinases encoded by genes adjacent to the fim gene cluster and little evidence to indicate the presence of a functional fimS
Because FimZ is related to the family of response regulators, we constructed mutants that would mimic constitutive phosphorylation and no phosphorylation phenotypes in vivo to examine their effect on fimA expression and fimbria production
Summary
The production of type 1 fimbriae in Salmonella enterica serovar Typhimurium is controlled, in part, by three proteins, FimZ, FimY, and FimW. Because FimZ is related to the family of response regulators, we constructed mutants that would mimic constitutive phosphorylation and no phosphorylation phenotypes in vivo to examine their effect on fimA expression and fimbria production. Mutated fimZ alleles were integrated onto the chromosome of SL1344⌬fimZ, and the mutants were examined for their ability to produce type 1 fimbriae.
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