Date of Award
Doctor of Philosophy (PhD)
This work is focused on iron trafficking through ABC transporters in Staphylococcus aureus and combatting the growing antimicrobial resistance crisis by exploiting virulence factors as therapeutic targets. Specifically, the goal was to understand the role of a siderophore-binding lipoprotein FhuD2 in S. aureus iron trafficking. While S. aureus endogenously produces three metallophores for metal sequestration from the host, FhuD2 is thought to scavenge metals from hydroxamate-based xenosiderophores encountered in the host environment. FhuD2 is a critical virulence factor and vaccine candidate (Novartis) for MRSA. Since xenosiderophore scavenging systems are often dispensable, it was hypothesized that FhuD2 must be playing another role to enhance pathogen virulence. Through careful investigations using a fluorescent siderophore probe, this work has revealed a new role for FhuD2 in the S. aureus iron trafficking pathway. FhuD2 does tightly bind hydroxamate xenosiderophores, but it does not immediately use the siderophore as a transport substrate. Instead, the siderophore serves as a cofactor for a newly proposed enzymatic function of FhuD2 in iron trafficking from human holo-transferrin. Using a “turn-off” fluorescent siderophore probe it was shown that the FhuD2 apo-siderophore complex is capable of catalyzing iron extraction from transferrin. The interaction of FhuD2 with transferrin better explains its role as a virulence factor and establishes a new paradigm for iron trafficking in bacteria with broad relevance. This same phenomenon was confirmed another human pathogen, Bacillus subtilis. Structure-activity relationship analysis of siderophores governing cell entry revealed a charge-based preference for whole cell uptake in S. aureus.
Chair and Committee
Timothy A. Wencewicz
John-Stephen Taylor, Meredith Jackrel, Jeffrey P. Henderson, Kevin D. Moeller,
Endicott, Nathaniel, "Siderophore-Dependent Transport Paradigms for Iron Across the Bacterial Cell Envelope in the Human Pathogen Staphylococcus aureus" (2019). Arts & Sciences Electronic Theses and Dissertations. 1899.