Sterols in yeast subcellular fractions

Area of Science:

• Cellular Biology
• Biochemistry
• Mycology

Background:

• Yeast synthesizes substantial sterols, crucial for cellular economy.
• Sterols exist as free sterols or esterified with fatty acids.
• Yeast's genetic tractability makes it ideal for studying sterol roles.

Purpose of the Study:

• Investigate the role of sterols in yeast cellular economy.
• Examine the effects of azasterol on yeast sterol synthesis and growth.
• Determine the relationship between respiratory competency and sterol biosynthesis.

Main Methods:

• Utilized azasterol, a naturally occurring antimycotic, to inhibit yeast growth and sterol synthesis.
• Analyzed effects on key sterol synthesis enzymes: delta14-reductase, sterol methyltransferase, and methylene reductase.
• Compared respiratory and phosphorylation capabilities in wild-type and mutant yeast strains using purified mitochondria.

Main Results:

• Azasterol inhibited yeast growth by targeting three sterol synthesis enzymes.
• Cells on respiratory substrates were more sensitive to azasterol inhibition than those on glucose.
• A link was established between respiratory competency and sterol biosynthesis; mutants often showed defects.
• Mutant yeast respired at higher temperatures but failed to couple respiration to phosphorylation.
• Yeast discriminates sterols, favoring ergosterol for mitochondrial inclusion.

Conclusions:

• Sterol biosynthesis is intricately linked to respiratory function in yeast.
• Azasterol effectively disrupts yeast sterol synthesis and impacts cellular respiration.
• Yeast exhibits selective incorporation of ergosterol into mitochondrial structures.