Accumulation of inorganic polyphosphates in <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> under nitrogen deprivation: Stimulation by magnesium ions and peculiarities of localization |
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Authors: | N A Breus L P Ryazanova N E Suzina N V Kulakovskaya A Ya Valiakhmetov V A Yashin V V Sorokin I S Kulaev |
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Institution: | (1) Skryabin Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, 142290 Pushchino, Moscow, Russia; |
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Abstract: | The yeast Saccharomyces cerevisiae was shown to have a high potential as a phosphate-accumulating organism under growth suppression by nitrogen limitation.
The cells took up over 40% of phosphate from the medium containing 30 mM glucose and 5 mM potassium phosphate and over 80%
of phosphate on addition of 5 mM magnesium sulfate. The major part of accumulated Pi was reserved as polyphosphates. The content
of polyphosphates was ∼57 and ∼75% of the phosphate accumulated by the cells in the absence and presence of magnesium ions,
respectively. The content of long-chain polyphosphates increased in the presence of magnesium ions, 5-fold for polymers with
the average length of ∼45 phosphate residues, 3.7-fold for polymers with the average chain length of ∼75 residues, and more
than 10-fold for polymers with the average chain length of ∼200 residues. On the contrary, the content of polyphosphates with
the average chain length of ∼15 phosphate residues decreased threefold. According to the data of electron and confocal microscopy
and X-ray microanalysis, the accumulated polyphosphates were localized in the cytoplasm and vacuoles. The cytoplasm of the
cells accumulating polyphosphates in the presence of magnesium ions had numerous small phosphorus-containing inclusions; some
of them were associated with large electron-transparent inclusions and the cytoplasmic membrane. |
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