1887

Abstract

The operons constitute four homologous regions in the genome, each of which has 8–13 ORFs. Although the function of the Mce protein family has not been clearly established, its members are believed to be membrane lipid transporters. Based on functional experiments, we found that the regulator of the locus, Mce3R, negatively regulates the expression of the and transcriptional units. These operons are adjacent to one another and divergently transcribed. The predicted functions of most of these genes are related to either lipid metabolism or redox reactions. Bioinformatic analysis of the 5′ UTR sequences of the differentially expressed genes allowed us to define a putative Mce3R motif. Importantly, the Mce3R motif was present six and three times in the and intergenic regions, respectively. Two occurrences of this motif mapped within the two regions of the operon that were protected by Mce3R in a footprinting analysis, thus indicating that this motif is likely to serve as an operator site for the Mce3R regulator in the promoter. In addition, alterations in the lipid content of were detected in the absence of Mce3R. Taken together, these results suggest that Mce3R controls the expression of both the putative transport system encoded in the operon and the enzymes implicated in the modification of the Mce3-transported substrates.

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2009-07-01
2019-10-15
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