Manganese accumulation in yeast cells. Electron-spin-resonance characterization and superoxide dismutase activity.
Manganese accumulation was studied by room-temperature electron spin resonance (ESR) spectroscopy in Saccharomyces cerevisiae grown in the presence of increasing amounts of MnSO4. Mn2+ retention was nearly linear in intact cells for fractions related to both low-molecular-mass and macromolecular complexes ('free' and 'bound' Mn2+, respectively). A deviation from linearity was observed in cell extracts between the control value and 0.1 mM Mn2+, indicating more efficient accumulation at low Mn2+ concentrations. The difference in slopes between the two straight lines describing Mn2+ retention at concentrations lower and higher than 0.1 mM, respectively, was quite large for the free Mn2+ fraction. Furthermore it was unaffected by subsequent dialyses of the extracts, showing stable retention in the form of low-molecular-mass complexes. In contrast, the slope of the line describing retention of 'bound' Mn2+ at concentrations higher than 0.1 mM became less steep after subsequent dialyses of the cell extracts. This result indicates that the macromolecule-bound Mn2+ was essentially associated with particulate structures. In contrast to Cu2+, Mn2+ had no effect on the major enzyme activities involved in oxygen metabolism except for a slight increase of cyanide-resistant Mn-superoxide dismutase activity, due to dialyzable Mn2+ complexes.
Galiazzo
F
F
Department of Biology, Tor Vergata University of Rome, Italy.
Pedersen
J Z
JZ
Civitareale
P
P
Schiesser
A
A
Rotilio
G
G
D004578:Electron Spin Resonance Spectroscopy; D008345:Manganese / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000378:metabolism*; D013696:Temperature
D008345:Manganese; D013482:Superoxide Dismutase