Role of FeoA: interaction with the Fe2+ -Fur complexAltwirgai, M. S. (2024) Role of FeoA: interaction with the Fe2+ -Fur complex. PhD thesis, University of Reading
It is advisable to refer to the publisher's version if you intend to cite from this work. See Guidance on citing. To link to this item DOI: 10.48683/1926.00119892 Abstract/SummaryThis project focusses on the role of ‘Feo’ (the FeoABC system of Escherichia coli), the major anaerobic bacterial ferrous iron uptake system, in the regulation of bacterial iron metabolism. Whereas the role of FeoB is well understood (ferrous permease), the purposes of the small, cytosolic FeoA and FeoC proteins remain unclear and there is a strong possibility that they have a regulatory function. In particular, the role of FeoA is intriguing since it is essential for Feo activity and is highly conserved and is homologous to a domain (SH3 domain) associated with a type of global iron regulator (DtxR-family members) found in high G+C Gram-positive bacteria. One possible role for FeoA is as an iron-dependent regulator of FeoB iron uptake activity. The hypothesis to be tested is that FeoA interacts with the Fe2+ -Fur complex (present when cytosolic levels of free iron are relatively high) but is released from apo-Fur (when iron levels are low) and instead binds to FeoB to activate its iron uptake activity. This hypothesis suggests that FeoA also modulates Fur-regulatory activity which would be relevant anaerobically, when the feoABC operon is induced. Here, this theory was investigated by initially studying the expression of the Fe-Fur regulated bfr, yncE and yqjH genes via semi-quantitative western blot analysis of the corresponding proteins Bfr, YncE and YqjH proteins in E. coli strains with mutations in feoA, feoB or feoC, both aerobically and anaerobically. No good evidence for FeoA in relieving Fur dependent gene control was obtained, although the iron chelator, BIP, impacted the abundance of these proteins in a fashion indicative of iron and Fur control. In addition, the feoA and feoB mutations caused expression-effects consistent with a reduction in iron-uptake activity, particularly anaerobically. To further determine whether FeoA plays a part in Fur-dependent gene control, the feoA and feoABC genes were induced from plasmids carrying the corresponding feo genes in arabinose inducible format and the impact on bfr and yqjH was monitored by western blotting under aerobic conditions in the wildtype and fur mutant, in the presence/absence of BIP. Again, clear iron/Fur dependent regulation was observed for both targets. Further, induction of feoABC caused a suppression of Bfr levels consistent with the hypothesis. Similarly, for YqjH, feoA induction stimulated an increase in levels in the first few hours of induction, which is also consistent with the hypothesis being explored.
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