Mario Rivera photoMario Rivera
Professor, Chemistry
The University of Kansas

Dynamics and Interactions in the Release of Iron Stored in Bacterioferritin (2010-2012)

The antibiotic resistance developed by bacteria is cause of public concern. A possible solution is to develop drugs that interfere with the handling of iron, a required nutrient. To approach this goal we plan to gain molecular understanding of the dynamic processes and inter-protein interactions that allow P. aeruginosa to store the toxic Fe2+ iron, and when needed, release it for its safe incorporation into metabolic paths that guarantee survival of the pathogen in a host.

Organisms that cause diseases such as respiratory tract infections (Haemophilus influenzae), enteric conditions (Shigella dysenteriae) and the opportunistic Pseudomonas aeruginosa have developed sophisticated mechanisms for sequestering iron from their host. This intense competition between invading pathogens and their host for the nutrient has led to the idea that new antimicrobials may target iron acquisition and homeostasis.

To approach more closely to this goal, it is important to gain molecular-level understanding of the mechanisms by which pathogens manage iron, from acquisition and internalization to storage and utilization. Significant advances have improved our understanding of iron uptake by P. aeruginosa and many other pathogens. In comparison, little is known about the fate of internalized iron. One mechanism whereby iron toxicity is controlled is by storage of iron in ferritin and bacterioferritin, which are large proteins capable of storing up to 4,000 iron atoms in their internal cavities. Despite the importance of ferritins and bacterioferritins in regulating iron concentrations and preventing its toxic effects, little is known about the processes that deliver Fe2+ for storage or the signals that prompt its release for safe integration in metabolism.

We have recently demonstrated that mobilization of Fe2+ from bacterioferritin A (BfrA) in P. aeruginosa requires electron transfer from a ferredoxin reductase (FPR). Thus the BfrA-FPR complex is an unprecedented opportunity to investigate how bacterioferritins recognize their physiological regulators and if binding modulates the dynamic properties of the bacterioferritin to facilitate iron release. To fill these gaps we plan to: (1) Investigate the dynamic properties of BfrA utilizing a strategy specifically tailored to study large proteins using hydrogen/deuterium H/D exchange coupled to NMR spectroscopy. (2) Investigate the dynamic properties of BfrA with the aid of computational methods and (3) Utilize computational and HD/NMR methods to investigate how BfrA binds to FPR and determine the effect that the inter-protein association exerts on the dynamic properties of BfrA.