Iron Content of Saccharomyces cerevisiae Cells Grown under Iron-Deficient and Iron-Overload Conditions

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• 作者：Gregory P. Holmes-Hampton ; Nema D. Jhurry ; Sean P. McCormick ; Paul A. Lindahl
• 刊名：Biochemistry
• 出版年：2013
• 出版时间：January 8, 2013
• 年：2013
• 卷：52
• 期：1
• 页码：105-114
• 全文大小：392K
• 年卷期：v.52,no.1(January 8, 2013)
• ISSN：1520-4995

文摘

Fermenting cells were grown under Fe-deficient and Fe-overload conditions, and their Fe contents were examined using biophysical spectroscopies. The high-affinity Fe import pathway was active only in Fe-deficient cells. Such cells contained 150 渭M Fe, distributed primarily into nonheme high-spin (NHHS) Fe^II species and mitochondrial Fe. Most NHHS Fe^II was not located in mitochondria, and its function is unknown. Mitochondria isolated from Fe-deficient cells contained [Fe₄S₄]²⁺ clusters, low- and high-spin hemes, S = ¹/₂ [Fe₂S₂]⁺ clusters, NHHS Fe^II species, and [Fe₂S₂]²⁺ clusters. The presence of [Fe₂S₂]²⁺ clusters was unprecedented; their presence in previous samples was obscured by the spectroscopic signature of Fe^III nanoparticles, which are absent in Fe-deficient cells. Whether Fe-deficient cells were grown under fermenting or respirofermenting conditions had no effect on Fe content; such cells prioritized their use of Fe to essential forms devoid of nanoparticles and vacuolar Fe. The majority of Mn ions in wild-type yeast cells was electron paramagnetic resonance-active Mn^II and not located in mitochondria or vacuoles. Fermenting cells grown on Fe-sufficient and Fe-overloaded medium contained 400鈥?50 渭M Fe. In these cells, the concentration of nonmitochondrial NHHS Fe^II declined 3-fold, relative to that in Fe-deficient cells, whereas the concentration of vacuolar NHHS Fe^III increased to a limiting cellular concentration of 300 渭M. Isolated mitochondria contained more NHHS Fe^II ions and substantial amounts of Fe^III nanoparticles. The Fe contents of cells grown with excessive Fe in the medium were similar over a 250-fold change in nutrient Fe levels. The ability to limit Fe import prevents cells from becoming overloaded with Fe.