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Mössbauer and EPR Study of Iron in Vacuoles from Fermenting Saccharomyces cerevisiae
- Source :
- Biochemistry. 50:10275-10283
- Publication Year :
- 2011
- Publisher :
- American Chemical Society (ACS), 2011.
-
Abstract
- Vacuoles were isolated from fermenting yeast cells grown on minimal medium supplemented with 40 μM (57)Fe. Absolute concentrations of Fe, Cu, Zn, Mn, Ca, and P in isolated vacuoles were determined by ICP-MS. Mössbauer spectra of isolated vacuoles were dominated by two spectral features: a mononuclear magnetically isolated high-spin (HS) Fe(III) species coordinated primarily by hard/ionic (mostly or exclusively oxygen) ligands and superparamagnetic Fe(III) oxyhydroxo nanoparticles. EPR spectra of isolated vacuoles exhibited a g(ave) ~ 4.3 signal typical of HS Fe(III) with E/D ~ 1/3. Chemical reduction of the HS Fe(III) species was possible, affording a Mössbauer quadrupole doublet with parameters consistent with O/N ligation. Vacuolar spectral features were present in whole fermenting yeast cells; however, quantitative comparisons indicated that Fe leaches out of vacuoles during isolation. The in vivo vacuolar Fe concentration was estimated to be ~1.2 mM while the Fe concentration of isolated vacuoles was ~220 μM. Mössbauer analysis of Fe(III) polyphosphate exhibited properties similar to those of vacuolar Fe. At the vacuolar pH of 5, Fe(III) polyphosphate was magnetically isolated, while at pH 7, it formed nanoparticles. This pH-dependent conversion was reversible. Fe(III) polyphosphate could also be reduced to the Fe(II) state, affording similar Mössbauer parameters to that of reduced vacuolar Fe. These results are insufficient to identify the exact coordination environment of the Fe(III) species in vacuoles, but they suggest a complex closely related to Fe(III) polyphosphate. A model for Fe trafficking into/out of yeast vacuoles is proposed.
- Subjects :
- biology
Iron
Inorganic chemistry
Saccharomyces cerevisiae
Electron Spin Resonance Spectroscopy
chemistry.chemical_element
Biological Transport
Vacuole
biology.organism_classification
Ferric Compounds
Biochemistry
Oxygen
Article
Yeast
law.invention
Spectroscopy, Mossbauer
chemistry
law
Vacuoles
Mössbauer spectroscopy
Fermentation
Electron paramagnetic resonance
Nuclear chemistry
Superparamagnetism
Subjects
Details
- ISSN :
- 15204995 and 00062960
- Volume :
- 50
- Database :
- OpenAIRE
- Journal :
- Biochemistry
- Accession number :
- edsair.doi.dedup.....2b01b75dc31e6b9939afe51a0d427155