Structure of the tubulin dimer

Area of Science:

• Cell Biology
• Biochemistry
• Structural Biology

Background:

• Microtubules are essential cytoskeletal components formed from tubulin dimers.
• Tubulin exists as alpha and beta monomers, theoretically forming homodimers or heterodimers.

Purpose of the Study:

• To investigate the native state of tubulin dimers (heterodimer vs. homodimer).
• To analyze the influence of aggregation and specific drugs on tubulin structure.

Main Methods:

• Chemical cross-linking of soluble chick brain tubulin using dimethyl-3,3-(tetramethylene dioxy) dipropionimidate dihydrochloride (DTDI).
• Analysis of cross-linked products via polyacrylamide gel electrophoresis to resolve dimer types (alphaalpha, alphabeta, betabeta).
• Assessment of aggregation and drug effects (colchicine, Vinca alkaloids) on cross-linking.

Main Results:

• Cross-linking predominantly yielded alphabeta heterodimers (60-90%), indicating this is the primary native form.
• Incubation at 24 degrees Celsius increased overall cross-linked dimer yield, suggesting tubulin aggregation over time.
• Increased alphaalpha and betabeta homodimers correlated with incubation time, supporting their origin from nonspecific aggregation.

Conclusions:

• Soluble tubulin primarily exists as alphabeta heterodimers.
• Homodimers (alphaalpha, betabeta) likely result from nonspecific aggregation during purification.
• Colchicine and Vinca alkaloids influence tubulin aggregation in a manner consistent with their effects on polymerization.