U.S. Department of Health and Human Services

Genetics and Metabolism Section

Caroline C. Philpott, M.D., Chief

​Research Images

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Color image depicting the process of iron homeostasis in yeastThis image depicts iron homeostasis in yeast. Proteins expressed as part of the Aft1 and 2 regulon are labeled in black text. The low affinity iron transporters Smf1 and Fet4 are also shown. Genes that are downregulated in iron deficiency are indicated in gray text.Enlarge
Color model depicting PCBP1 delivering iron to ferritinThis image depicts a model of PCBP1 delivering iron to ferritin. PCBP1 binds 3 Fe(II) ions and binds to ferritin, delivering the iron for mineralization of the ferritin core.Enlarge
Color image depicting PCBP iron chaperones in mammalian cellsThis image depicts circulating iron binds to transferrin (Tf), which binds to transferrin receptor (TfR) on the cell surface. Endocytosis internalizes ferric Tf/TfR complex and transferrin releases iron reduced to ferrous form. DMT1 transports ferrous iron to the cytosol. PCBP iron chaperones deliver it to cytosolic iron enzymes. Iron also transfers to mitochondria.Enlarge
Heme homeostasis in the eukaryotic cell is a balance of synthesis, distribution, and degradation.This is a simplified scheme of heme homeostasis in the eukaryotic cell. The final step of heme biosynthesis, the ferrochelatase (FECH) reaction, takes place in the mitochondria. Newly synthesized heme is used for assembly of cytochomes (CytC) and other heme proteins located in the cytoplasm, endoplasmic reticulum (ER), lysosomes, and nucleus. The degradation of heme to the iron, biliverdin (BV), and carbon monoxide is catalyzed by heme oxygenase associated with the ER. Heme uptake and heme export are mediated by the function of the plasma membrane heme transporters. Question marks signal unexplored pathways of intracellular heme transfer.Enlarge
Yeast heme oxygenase Hmx1 regulates heme homeostasisThis is an indirect Immunofluorescence image of Hmx1 in a yeast cell. Hmx1 is localized to the endoplasmic reticulum, a ring-like structure around the nucleus and periphery of the cell. Hmx1-HA was detected with (a) an anti-HA antibody, (b) a nucleus stained with DAPI, and (c) a merged image.Enlarge
Yeast as a tool to study heme transporters from other species.A yeast strain deficient in heme synthesis (hem1) can only grow when media are supplemented with heme precursor, 5-aminolevulinic acid (ALA), or a high concentration of heme. Expression of the heme transporter HRG4 from the worm C.elegans allows yeast to grow at low heme concentration.Enlarge