Alterations in number of protofilaments in microtubules assembled in vitro

Area of Science:

• Biochemistry
• Cell Biology
• Structural Biology

Background:

• Tubulin is the main protein component of microtubules, essential cytoskeletal structures in eukaryotic cells.
• Microtubule assembly is a dynamic process influenced by various in vitro conditions.
• The protofilament number in microtubule walls can vary, impacting microtubule structure and function.

Purpose of the Study:

• To investigate the in vitro polymerization of bovine brain tubulin under diverse assembly conditions.
• To determine the protofilament number in microtubules formed during these experiments.
• To assess the effect of repeated cold-dissociation and reassembly cycles on microtubule protofilament structure.

Main Methods:

• Purification of tubulin from bovine brain.
• In vitro polymerization of tubulin under varied conditions.
• Analysis of microtubule structure, specifically counting wall protofilaments using electron microscopy.
• Repeated cycles of cold-induced microtubule dissociation and subsequent in vitro reassembly.

Main Results:

• A significant proportion of polymerized microtubules exhibited 14 wall protofilaments.
• The number of microtubules with 14 protofilaments increased with successive rounds of cold-dissociation and reassembly.
• Assembly conditions influenced the resulting microtubule structures.

Conclusions:

• Bovine brain tubulin can form microtubules with a predominant 14-protofilament structure in vitro.
• Repeated cycles of depolymerization and repolymerization favor the formation of 14-protofilament microtubules.
• This suggests a potential structural preference or stabilization of the 14-protofilament lattice under specific experimental conditions.