Microtubules are formed from a 110,000-dalton dimeric subunit called tubulin. Two forms of 55,000-dalton monomer, α and β, are found in all microtubule preparations. The dimers could thus theoretically be either heterodimers (αβ) or homodimers (αα and ββ). This problem was investigated by chemical cross-linking using several bifunctional reagents, of which one, dimethyl-3,3'-(tetramethylenedioxy) dipropionimidate dihydrochloride (DTDI), was able to make intradimer bonds in tubulin. When soluble chick brain tubulin was cross-linked with DTDI and analyzed by electrophoresis in an acrylamide gel system capable of resolving αα, αβ, and ββ, 60 to 90% of the cross-linked dimer was αβ. If tubulin was incubated at 24° prior to cross-linking with DTDI the total yield of cross-linked dimer increased with time, indicating that tubulin was forming loose aggregates. The relative amounts of cross-linked αα and ββ also increase with time, indicating that soluble tubulin is largely αβ, and suggesting that cross-linked αα and ββ arise from nonspecific aggregation during tubulin purification. The aggregation observed by cross-linking with DTDI was strongly influenced by colchicine and Vinca alkaloids in a pattern similar to the effects of these drugs on tubulin polymerization.
|Original language||English (US)|
|Number of pages||9|
|Journal||Journal of Biological Chemistry|
|State||Published - 1977|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology