Isolation and characterization of polyphosphates from the yeast cell surface

Area of Science:

• Cellular Biology
• Biochemistry

Background:

• Inorganic polyphosphates (polyP) are ubiquitous polymers with diverse cellular roles.
• Understanding polyP localization and metabolism is crucial for elucidating their functions.

Purpose of the Study:

• To investigate the characteristics of inorganic polyphosphate released by Saccharomyces fragilis under osmotic stress.
• To determine the cellular localization and metabolic properties of this specific polyP fraction.

Main Methods:

• Subjecting Saccharomyces fragilis cells to osmotic shock.
• Assessing cell viability, K+ leakage, and cell staining to evaluate membrane integrity.
• Analyzing the mean chain length and metabolic turnover rate ([32P]orthophosphate pulsing) of released polyP.
• Using anion exchange chromatography (Dowex AG 1-X4) to isolate polyphosphates.

Main Results:

• Osmotic shock induced the release of approximately 10% of total cellular inorganic polyphosphate.
• The released polyP fraction exhibited significantly higher mean chain length and lower metabolic turnover compared to intracellular polyP.
• Minimal membrane damage was observed, suggesting extracellular localization of the released polyP.
• Anion exchange resin treatment also released high molecular weight polyphosphates.

Conclusions:

• A specific fraction of inorganic polyphosphate in Saccharomyces fragilis is sensitive to osmotic shock and localized outside the plasma membrane.
• This shock-sensitive polyP fraction possesses distinct characteristics regarding chain length and metabolic activity.
• These findings highlight specific cellular localization and metabolic properties of osmotically labile polyphosphates.