Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/20/2007
Publication Date: 5/20/2007
Citation: Janagama, H.K., Bannantine, J.P., Rodriguez, M., Smith, I., Sreevatsan, S. 2007. Identification and Characterization of Iron Dependent Regulator (IdeR) of Mycobacterium avium subsp. paratuberculosis [abstract]. Poster #275. Interpretive Summary:
Technical Abstract: Mycobacterium avium subsp. paratuberculosis (MAP), is known for its dependency on mycobactin for its growth in laboratory media. Comparative genomics of M. tuberculosis, M. avium subsp. paratuberculosis and M. avium avium showed that mycobactin A, a gene encoding the first enzyme of mycobactin synthesis is truncated in MAP. Thus we hypothesized that alternate iron regulation mechanisms may be utilized by MAP. Toward this end, we initiated studies on the well-established Iron Dependent Regulator (IdeR), a transcriptional factor that plays a global iron regulatory role in Mycobacterium tuberculosis (MTB) with a 19-bp recognition sequence termed, iron box. We used a bioinformatics approach that utilized the Prokaryotic Database of Gene Regulation (PRODORIC) to predict the 19-bp iron-box sequences within the MAP genome and identified several genes that are potentially regulated by IdeR. Computational predictions identified IdeR recognition sites located upstream of genes involved in iron transport, iron storage, siderophore synthesis, other transcriptional regulators and oxidative stress response genes. The intergenic regions of these putative IdeR regulated genes that included the iron box sequence were amplified and binding was confirmed in gel retardation assays. This IdeR-iron box binding was not heavy metal dependent. Theoretical tertiary structure prediction of IdeR was consistent with the finding that very low molar quantity of iron is sufficient for IdeR-iron box binding. This is expected to confer a selective advantage to MAP owing to its defective mycobactin synthesis machinery. Theoretical structural predictions further identified IdeR as an analogous protein to IdeR of MTB suggesting a possible divergence during evolution. DNAse foot printing assay identified that IdeR protects a 30 base pair intergenic region consisting of the 19-bp iron box sequence. In sum, we identified that IdeR of MAP is a transcriptional factor and recognizes the predicted iron box sequence suggesting a role in iron regulation of MAP. Further studies to create IdeR deletion mutant and characterize IdeR regulon are underway.