Title
Metabolite Driven Regulation of Heme Uptake by the Biliverdin IXβ/δ Selective HemO of Pseudomonas aeruginosa.
Author
Susana Mourino, Bennett J. Giardina, Hermes Reyes-Caballero, Angela Wilks
Year
2016
Journal
The Journal of Biological Chemistry
Abstract
Pseudomonas aeruginosa acquires extracellular heme via the Phu (Pseudomonas heme uptake) and Has (heme assimilation system) systems. We have previously shown the catalytic action of heme oxygenase HemO along with the cytoplasmic heme transport protein PhuS control heme flux into the cell. To further investigate the role of the PhuS-HemO couple in modulating heme uptake we have characterized two HemO variants, one that is catalytically inactive (HemO H26A/K34A/K132A or HemOin) and one that has altered regioselectivity (HemO N19K/K34A/ F117Y/K132A or HemOα), producing biliverdin IXα (BVIXα). HemOα similar to wild type was able to interact and acquire heme from holo-PhuS. In contrast the HemOin variant did not interact with holo-PhuS and showed no enzymatic activity. Complementation of a hemO deletion strain with the hemOin or hemOα variants in combination with 13C-heme isotopic labeling experiments, revealed the absence of BVIXβ and BVIXδ leads to a decrease in extracellular levels of hemophore HasA. We propose BVIXβ and/or BVIXδ transcriptionally or post-transcriptionally regulate HasA. Thus coupling the PhuS dependent flux of heme through HemO to feedback regulation of the cell surface signaling system (CSS) through HasA allows P. aeruginosa to rapidly respond to fluctuating extracellular heme levels independent of the iron status of the cell.
Instrument
J-810
Keywords
Circular dichroism, Secondary structure, Thermal stability, Protein denaturation, Thermodynamics, Biochemistry