Structural and functional differences between porcine brain and budding yeast microtubules

Area of Science:

• Cell Biology
• Biochemistry
• Structural Biology

Background:

• Microtubules, crucial components of the eukaryotic cytoskeleton, are assembled from tubulin proteins.
• Previous research indicated sequence and structural conservation of tubulin across species, yet functional differences exist between mammalian and yeast microtubules.

Purpose of the Study:

• To compare the structure and function of microtubules assembled from mammalian (porcine) and budding yeast tubulin.
• To investigate how subtle sequence variations in tubulin influence microtubule assembly dynamics and interactions.

Main Methods:

• In vitro assembly of microtubules from yeast and porcine tubulin.
• Analysis of microtubule protofilament number and geometry using structural methods.
• Assessment of tubulin oligomer formation and curvature in solution.
• Testing species-specific binding of EB proteins (Bim1 and EB1) to microtubules.

Main Results:

• Significant differences were observed in the protofilament number distribution of yeast and porcine microtubules.
• Yeast tubulin formed longer, less curved oligomers in solution, indicating stronger intra-protofilament interactions.
• Yeast EB1 (Bim1) specifically tracked yeast microtubules, while human EB1 tracked mammalian microtubules, demonstrating species-specific plus-end tracking.

Conclusions:

• Subtle sequence differences in tubulin subunits lead to significant structural and functional divergence in microtubules.
• These findings highlight the impact of tubulin sequence variation on microtubule assembly, stability, and regulation by associated proteins.