Dr. Angela Wilks
Department of Pharmaceutical Sciences, School of Pharmacy
University of Maryland, Baltimore
February 24th, 2017 – Spring Seminar
Time and location: Noon at Chem 120
Host: Dr. Aaron Smith
Abstract
The opportunistic pathogen P. aeruginosa encode two extracellular heme uptake systems, the Pseudomonas heme uptake (phu) and the heme assimilation system (has). Consistent with recent studies indicating PhuR as the primary heme receptor in clinical infection, our laboratory has shown Phu system is the major heme transporter with the hemophore dependent Has system acting primarily in heme sensing. 13C-heme isotropic labeling and bacterial genetics combined with biochemical and biophysical studies further show the intracellular heme chaperone PhuS is critical in linking heme flux through the biliverdin ΙΧβ and ΙΧδ regioselective HemO to post-transcriptional regulation of heme utilization. Complementation of the ΔhemO deletion strain with a BVIX-α selective (hemOα) or a catalytically inactive (hemOin) hemO mutant down regulates expression of the hemophore HasΑ and its cognate receptor HasR. Mechanistic aspects the PhuS-HemO coupled regulation of heme flux have been studied by in vitro and in vivo methods employing hydrogen deuterium exchange (HDX) mas spectrometry techniques combined with resonance Raman spectroscopy. Furthermore, we present the first evidence for BVIXbeta-dependent post-transcriptional regulation of the ECF sigma-factor heme dependent cell surface signaling system. Coupling the regioselective metabolic flux of theme through PhuS-HemO with the extracellular heme sensing and regulatory network, provides a novel mechanism for the cell to rapidly respond and adapt to changes in extracellular heme and iron availability.
Related Articles:
Mouriño, Susana, et al. “Metabolite-driven Regulation of Heme Uptake by the Biliverdin IXβ/δ-Selective Heme Oxygenase (HemO) of Pseudomonas aeruginosa.” Journal of Biological Chemistry 291.39 (2016): 20503-20515.
O’Neill, Maura J., et al. “Induced fit on heme binding to the Pseudomonas aeruginosa cytoplasmic protein (PhuS) drives interaction with heme oxygenase (HemO).” Proceedings of the National Academy of Sciences 109.15 (2012): 5639-5644.