title: Biophysical investigation of the iron in Aft1-1(up) and Gal-YAH1 Saccharomyces cerevisiae.
abstract: Aft1p is a major iron regulator in budding yeast Saccharomyces cerevisiae. It indirectly senses cytosolic Fe status and responds by activating or repressing iron regulon genes. Aft1p within the Aft1-1(up) strain has a single amino acid mutation which causes it to constitutively activate iron regulon genes regardless of cellular Fe status. This leads to elevated Fe uptake under both low and high Fe growth conditions. Ferredoxin Yah1p is involved in Fe/S cluster assembly, and Aft1p-targeted iron regulon genes are also upregulated in Yah1p-depleted cells. In this study Mössbauer, EPR, and UV-vis spectroscopies were used to characterize the Fe distribution in Aft1-1(up) and Yah1p-depleted cells. Aft1-1(up) cells grown in low Fe medium contained more Fe than did WT cells. A basal level of Fe in both WT and Aft1-1(up) cells was located in mitochondria, primarily in the form of Fe/S clusters and heme centers. The additional Fe in Aft1-1(up) cells was present as mononuclear HS Fe(III) species. These species are in a nonmitochondrial location, assumed here to be vacuolar. Aft1-1(up) cells grown in high Fe medium contained far more Fe than found in WT cells. The extra Fe was present as HS Fe(III) ions, probably stored in vacuoles, and as Fe(III) phosphate nanoparticles, located in mitochondria. Yah1p-deficent cells also accumulated nanoparticles in their mitochondria, but they did not contain HS Fe(III) species. Results are interpreted by a proposed model involving three homeostatic regulatory systems, including the Aft1 system, a vacuolar iron regulatory system, and a mitochondrial Fe regulatory system.
authors.affiliation: Department of Chemistry, Texas A&M University, College Station, Texas 77843-3255, United States.
authors.forename: Ren
authors.initials: R
authors.lastname: Miao
authors.forename: Gregory P
authors.initials: GP
authors.lastname: Holmes-Hampton
authors.forename: Paul A
authors.initials: PA
authors.lastname: Lindahl
mesh_terms: D000325:Adrenodoxin / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D002570:Ceruloplasmin / Q000235:genetics / Q000378:metabolism; D055598:Chemical Phenomena; D004578:Electron Spin Resonance Spectroscopy; D038181:FMN Reductase / Q000235:genetics / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D007501:Iron / Q000378:metabolism*; D050296:Microbial Viability; D008928:Mitochondria / Q000378:metabolism; D008954:Models, Biological; D012333:RNA, Messenger / Q000378:metabolism; D018085:Regulon; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D015204:Spectroscopy, Mossbauer; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism
chemical_list: C090297:AFT1 protein, S cerevisiae; D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C120375:YAH1 protein, S cerevisiae; D000325:Adrenodoxin; D007501:Iron; D002570:Ceruloplasmin; C085513:FET3 protein, S cerevisiae; D038181:FMN Reductase; C023903:ferric citrate iron reductase