The role of the cytoplasmic heme-binding protein (PhuS) of Pseudomonas aeruginosa in intracellular heme trafficking and iron homeostasis.
The cytoplasmic heme-binding protein PhuS, encoded within the Fur-regulated Pseudomonas heme utilization (phu) operon, has previously been shown to traffic heme to the iron-regulated heme oxygenase (HO). We further investigate the role of PhuS in heme trafficking to HO on disruption of the phuS and hemO genes in a Pseudomonas aeruginosa siderophore-deficient and wild-type background. Previous studies have shown that deletion of hemO prevents the cells from utilizing heme as the sole source of iron. However, disruption of phuS alone resulted in a slow growth phenotype, consistent with its role as a heme-trafficking protein to HO. Furthermore, in contrast to the hemO and hemO/phuS deletion strains, the phuS knockout prematurely produced pyocyanin in the presence of heme. Western blot analysis of PhuS protein levels in the wild-type strain showed that Fur-regulation of the phu operon could be derepressed in the presence of heme. In addition the premature onset of pyocyanin production requires both heme and a functional HO. Suppression of the phenotype on increasing the external heme concentration suggested that the decreased heme-flux through HO results in premature production of pyocyanin. The premature production of pyocyanin was not due to lower intracellular iron levels as a result of decreased heme flux through HO. However, transcriptional analysis of the phuS mutants indicates that the cells are sensing iron deprivation. The present data suggest that PhuS has a dual function in trafficking heme to HO, and in directly or indirectly sensing and maintaining iron and heme homeostasis.
Kaur
Ajinder P
AP
Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201-1140.
Lansky
Ila B
IB
Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201-1140.
Wilks
Angela
A
Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201-1140. Electronic address: awilks@rx.umaryland.edu.
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000502:physiology; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D006418:Heme / Q000378:metabolism*; D006419:Heme Oxygenase (Decyclizing) / Q000235:genetics / Q000378:metabolism; D000081062:Heme-Binding Proteins; D006420:Hemeproteins / Q000235:genetics / Q000378:metabolism*; D006706:Homeostasis / Q000502:physiology; D007501:Iron / Q000378:metabolism; D009876:Operon / Q000502:physiology; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000378:metabolism*; D011710:Pyocyanine / Q000096:biosynthesis / Q000235:genetics
D001426:Bacterial Proteins; D002352:Carrier Proteins; D000081062:Heme-Binding Proteins; D006420:Hemeproteins; D006418:Heme; D011710:Pyocyanine; D007501:Iron; D006419:Heme Oxygenase (Decyclizing)