Affiliation:
1. Department of Biology, University of Utah, Salt Lake City, Utah 84112
Abstract
ABSTRACT
The flagellin gene
fliC
encodes the major component of the flagellum in
Salmonella enterica
serovar Typhimurium. This study reports the identification of a signal within the 5′ untranslated region (5′UTR) of the
fliC
transcript required for the efficient expression and assembly of FliC into the growing flagellar structure. Primer extension mapping determined the transcription start site of the
fliC
flagellin gene to be 62 bases upstream of the AUG start codon. Using
tetA-fliC
operon fusions, we show that the entire 62-base 5′UTR region of
fliC
was required for sufficient
fliC
mRNA translation to allow normal FliC flagellin assembly, suggesting that translation might be coupled to assembly. To identify sequence that might couple
fliC
mRNA translation to FliC secretion, the 5′ end of the chromosomal
fliC
gene was mutagenized by PCR-directed mutagenesis. Single base sequences important for
fliC
-dependent transcription, translation, and motility were identified by using
fliC-lacZ
transcriptional and translational reporter constructs. Transcription-specific mutants identified the −10 and −35 regions of the consensus flagellar class 3 gene promoter. Single base changes defective in translation were located in three regions: the AUG start codon, the presumed ribosomal binding site region, and a region near the very 5′ end of the
fliC
mRNA that corresponded to a potential stem-loop structure in the 5′UTR. Motility-specific mutants resulted from base substitutions only in the
fliC
-coding region. The results suggest that
fliC
mRNA translation is not coupled to FliC secretion by the flagellar type III secretion system.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
25 articles.
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