The heterotrimeric GTP-binding regulatory proteins (G proteins) play an important role in the regulation of membrane signal transduction. Recently, we identified the association of Go protein with mitotic spindles. Here we have investigated the relationship between Go protein and microtubules. We used temperature-dependent reversible assembly and taxol methods to purify microtubules from bovine brains. Goα and Gβ proteins were identified in the microtubular fraction by both methods. The Goα subunit in the microtubular fraction could be ADP ribosylated by pertussis toxin. Co-immunoprecipitation data also revealed that Go protein can interact with microtubules. Exogenous Go protein could be incorporated into the assembled microtubular fraction, and 5 µg/ml (60 nM) of Go protein inhibited 40% of microtubule assembly. Western blot analysis of Goα-1 and Goα-2 in microtubular fractions showed that only Goα-1 is associated with microtubules. We conclude that the Goα-1βγ proteins are associated with microtubules and may play some role in regulating the assembly and disassembly of microtubules.

Keywords:
ADP-ribosylation, Co-immunoprecipitation, Goα, Heterotrimeric Go protein, Microtubule, Tubulin
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© 2001 National Science Council, ROC and S. Karger AG, Basel
2001
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