expressed from two separate promoters . Our findings further indicate that transcription under iron-starvation can be controlled by Fur indirectly, as was observed for the dsbA1 gene. The sophisticated mechanism regulating dsb gene transcription in response to iron availability may be responsible for subtle changes in the abundance and/or activity of various selleck substrates in the Dsb system. We demonstrated that activity of C. jejuni 81-176 AstA, which is a direct target of Dsb system, is dependent on iron level in the medium. However, as AstA level is dependent on the activities of both DsbA1 and DsbA2 (unpublished results), details of the process remain unclear. Recently performed comparative Helicobacter pylori and Neisseria gonorrhoeae transcriptomic analysis also indicated that genes included in the Fur regulon
can be positively or negatively regulated in response to iron availability [38, 48]. Like C. jejuni Fur, H. pylori Fur also binds to some promoters in its iron-free form to repress their expression [38, 49–51]. C. jejuni Fur reveals a relatively high degree of amino acid identity with H. pylori Fur. Nonetheless it is not able to complement apo-Fur regulation in an H. pylori fur mutant when delivered in trans . Such unexpected results might be due to subtle differences in conformation of both proteins. Additional experiments, such as solving the three dimensional structure of C. jejuni Fur, are required to clarify CB-5083 the functional differences between Fur proteins of these closely related species. Although both species have AT-rich genomes and some of their promoters have similar structure, it can not be excluded that the C. jejuni apo-Fur binding nucleotide sequences are not identical as those determined for H. pylori apo-Fur. Thalidomide Also two H. pylori promoters, the pfr and sod gene promoters that are repressed by apo-Fur, exhibited low sequence similarity and revealed different affinities for apo-Fur [38, 50]. The second part of our research was aimed at understanding the relationship between dba and dsbI expression.
SB525334 solubility dmso Experiments employing point mutated dba provided evidence for strong translational coupling of the dba and dsbI genes. Inhibition or premature termination of dba mRNA translation resulted in the lack of DsbI. This defect was not complemented by the intact chromosomal dba gene in C. jejuni 81-176 dsbI::cat. Translational coupling has already been described and is common among functionally related bacterial genes. It was documented that in many cases it involves operons containing overlapping genes as well as genes constituting an operon and divided by short intergenic region [53, 54]. C. jejuni 81-176 dba and dsbI do not overlap, but are separated by a relatively short intergenic region (11 bp). Experiments employing a recombinant plasmid that expressed only DsbI verified the importance of the dba-dsbI mRNA secondary structure for its translation.