Purification and polymerization properties of two lethal yeast actin mutants

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Actin is essential for growth in Saccharomyces cerevisiae.
• Understanding actin function requires studying mutant variants.

Purpose of the Study:

• To characterize two yeast actin mutants (Glu334Lys and Gly168Arg) that impair cell growth.
• To elucidate the molecular mechanisms behind the growth defects.

Main Methods:

• Preparation of yeast actin mutants via coexpression with wild-type actin.
• Purification of mutant and wild-type actin using Ni-NTA chromatography.
• Analysis of actin polymerization kinetics and critical concentrations.

Main Results:

• The Glu334Lys mutant exhibited faster polymerization, indicating impaired interactions with actin binding proteins.
• The Gly168Arg mutant showed similar polymerization rates but reduced extent, suggesting a high critical concentration.
• These mutations, based on Caenorhabditis elegans actin mutant phenotypes, were located on actin surfaces and filament contacts.

Conclusions:

• The Glu334Lys mutation's defect is likely due to disrupted actin binding protein interactions.
• The Gly168Arg mutation affects the nucleation-elongation process by increasing the critical concentration.
• These findings provide insights into the structure-function relationships of actin in yeast.