Stereochemically distinct roles for sterol in Saccharomyces cerevisiae

Area of Science:

• Biochemistry
• Cell Biology
• Microbiology

Background:

• Sterols are vital for yeast growth, particularly under oxygen-deprived conditions.
• A specific 24 beta-methylsterol is essential for wild type Saccharomyces cerevisiae growth when 2,3-iminosqualene is present.

Purpose of the Study:

• To investigate the structural requirements of sterols for growth in Saccharomyces cerevisiae.
• To determine if sterols lacking the 24 beta-methyl group can fulfill the essential role of 24 beta-methylsterol.

Main Methods:

• Supplementation of oxygen-deprived wild type Saccharomyces cerevisiae cultures with various sterols.
• Growth assessment of yeast in the presence of different sterol formulations and 2,3-iminosqualene.

Main Results:

• Sterols like cholesterol, sitosterol, and 5 alpha-cholestan-3 beta-ol, lacking a 24 beta-methyl group, can partially replace the essential 24 beta-methylsterol.
• The essentiality of the 24 beta-methyl group is not absolute, indicating alternative sterol functions.
• Sterols without the 24 beta-methyl group can support the bulk membrane role, but not a potentially regulatory role.

Conclusions:

• Saccharomyces cerevisiae utilizes sterols in at least two distinct functional roles.
• One role, likely regulatory, necessitates the 24 beta-methyl group.
• The other role, a bulk membrane function, can be performed by various sterols, including those lacking the 24 beta-methyl group.