Yeast actin is relatively well behaved

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Yeast actin polymerization properties have been reported as unusual.
• Previous studies suggested intrinsic calcium-dependent properties of yeast actin.

Purpose of the Study:

• To develop a high-yield purification procedure for Saccharomyces cerevisiae actin.
• To characterize the polymerization properties of purified yeast actin.
• To investigate the interactions of yeast actin with yeast profilin and tropomyosin.

Main Methods:

• Developed a simple, sensitive spot assay for actin detection.
• Established a high-yield purification protocol for yeast actin.
• Characterized actin polymerization and interactions with actin-binding proteins.

Main Results:

• Purified yeast actin exhibits polymerization properties quantitatively similar to other characterized actins.
• Yeast profilin effectively sequesters yeast actin monomers, inhibiting polymerization.
• Yeast and smooth muscle tropomyosin bind similarly to yeast and rabbit skeletal muscle actin.
• Purified actin lacks the previously reported Ca2+-dependent increase in critical concentration.

Conclusions:

• The unusual Ca2+-dependent properties reported for yeast actin are likely due to minor contaminants.
• Purified yeast actin provides a reliable model for studying actin dynamics and interactions with yeast-specific actin-binding proteins.
• Yeast profilin plays a significant role in regulating yeast actin polymerization.