Miao, Ren (2010-12). Probing Iron Accumulation in Sacchromyces cerevisiae Using Integrative Biophysical and Biochemical Techniques. Doctoral Dissertation. Thesis uri icon

abstract

  • Iron is an essential element for life. It is involved in a number of biological processes, including iron sulfur (Fe/S) cluster assembly and heme biosynthesis. However it is also potentially toxic due to its ability to induce formation of reactive oxygen species (ROS) via Fenton chemistry. Therefore its uptake, trafficking and utilization must be regulated to avoid its toxicological effect. It has been recently discovered that Fe/S cluster biosynthesis machinery plays a key role in the cellular iron regulation and its disruption leads to impaired iron regulation and iron accumulation within mitochondria. The iron accumulation resulted from impaired Fe/S cluster assembly in the eukaryotic model organism Saccharomyces cerevisiae (baker's yeast) was studied. Various biophysical (e.g. M?ssbauer, EPR, UV-vis spectroscopy) and biochemical (e.g. Western blots, PCR, enzyme activity assay, etc.) techniques were used to characterize the iron content in yeast mitochondria isolated from several mutants strains. In these mutants one of the proteins involved in Fe/S cluster biosynthesis (Yah1p and Atm1p) is mutated and iron regulation and metabolism are disrupted. By integrating the results obtained from these different methods, it was determined that excess iron accumulates in the mutant mitochondria as inorganic phosphate Fe(III) nano-particles exhibiting superparamagnetic behaviors. Oxygen is required for iron accumulation and nanoparticle formation. The Fe(III) nano-particles can be chemically reduced to Fe(II) then largely exported from the mitochondria. These biophysical and biochemical methods were also used to examine the iron distribution in whole yeast cells of the Aft1-1up strain in which iron regulon genes are constitutively activated and compared to that of Yah1p-depleted and wild type yeast. Constitutive activation of iron regulon genes does not alter the cellular iron distribution significantly. However disruption of Fe/S cluster assembly by Yah1p depletion causes dramatic cellular iron redistribution: the vacuolar iron is largely evacuated and most of the cellular iron probably precipitates in mitochondria as Fe(III) nanoparticles. The results provide novel insights into iron trafficking and possible signal communications between organelles within cells.
  • Iron is an essential element for life. It is involved in a number of biological
    processes, including iron sulfur (Fe/S) cluster assembly and heme biosynthesis. However
    it is also potentially toxic due to its ability to induce formation of reactive oxygen
    species (ROS) via Fenton chemistry. Therefore its uptake, trafficking and utilization
    must be regulated to avoid its toxicological effect. It has been recently discovered that
    Fe/S cluster biosynthesis machinery plays a key role in the cellular iron regulation and
    its disruption leads to impaired iron regulation and iron accumulation within
    mitochondria.
    The iron accumulation resulted from impaired Fe/S cluster assembly in the
    eukaryotic model organism Saccharomyces cerevisiae (baker's yeast) was studied.
    Various biophysical (e.g. M?ssbauer, EPR, UV-vis spectroscopy) and biochemical (e.g.
    Western blots, PCR, enzyme activity assay, etc.) techniques were used to characterize the
    iron content in yeast mitochondria isolated from several mutants strains. In these mutants
    one of the proteins involved in Fe/S cluster biosynthesis (Yah1p and Atm1p) is mutated and iron regulation and metabolism are disrupted. By integrating the results obtained
    from these different methods, it was determined that excess iron accumulates in the
    mutant mitochondria as inorganic phosphate Fe(III) nano-particles exhibiting
    superparamagnetic behaviors. Oxygen is required for iron accumulation and nanoparticle
    formation. The Fe(III) nano-particles can be chemically reduced to Fe(II) then largely
    exported from the mitochondria.
    These biophysical and biochemical methods were also used to examine the iron
    distribution in whole yeast cells of the Aft1-1up strain in which iron regulon genes are
    constitutively activated and compared to that of Yah1p-depleted and wild type yeast.
    Constitutive activation of iron regulon genes does not alter the cellular iron distribution
    significantly. However disruption of Fe/S cluster assembly by Yah1p depletion causes
    dramatic cellular iron redistribution: the vacuolar iron is largely evacuated and most of
    the cellular iron probably precipitates in mitochondria as Fe(III) nanoparticles. The
    results provide novel insights into iron trafficking and possible signal communications
    between organelles within cells.

publication date

  • December 2010