Tubulin dimer formation via the release of α‐ and β‐tubulin monomers from multimolecular complexes

Abstract

The functional subunit of microtubules is a heterodimer consisting of α‐ and β‐tubulin. An understanding of tubulin dimerization has been hampered because it has not proved possible to purify native tubulin monomers. To study the process whereby tubulin dimers are formed, we made use of tubulins synthesized by in vitro transcription and translation. We present evidence that the in vitro synthesis of different mouse α‐tubulin isotypes involves a multimolecular complex. The synthesis of mouse β‐tubulin isotypes also involves the formation of multimolecular complexes, though different isotypes behave somewhat differently from one another. The properties of in vitro synthesized α‐ and β‐tubulin multimolecular complexes strongly suggest that they are intermediates in the biosynthesis of tubulin monomers. Upon release, these monomers can exchange with pre‐existing tubulin heterodimers.