The structure of the complex between alpha-tubulin, TBCE and TBCB reveals a tubulin dimer dissociation mechanism.Serna, M., Carranza, G., Martin-Benito, J., Janowski, R., Canals, A., Coll, M., Zabala, J.C., Valpuesta, J.M.
(2015) J.Cell.Sci. 128: 1824-1834
- PubMed: 25908846
- DOI: 10.1242/jcs.167387
- Primary Citation of Related Structures:
- PubMed Abstract:
Tubulin proteostasis is regulated by a group of molecular chaperones termed tubulin cofactors (TBC). Whereas tubulin heterodimer formation is well-characterized biochemically, its dissociation pathway is not clearly understood. Here, we carried out b ...
Tubulin proteostasis is regulated by a group of molecular chaperones termed tubulin cofactors (TBC). Whereas tubulin heterodimer formation is well-characterized biochemically, its dissociation pathway is not clearly understood. Here, we carried out biochemical assays to dissect the role of the human TBCE and TBCB chaperones in α-tubulin-β-tubulin dissociation. We used electron microscopy and image processing to determine the three-dimensional structure of the human TBCE, TBCB and α-tubulin (αEB) complex, which is formed upon α-tubulin-β-tubulin heterodimer dissociation by the two chaperones. Docking the atomic structures of domains of these proteins, including the TBCE UBL domain, as we determined by X-ray crystallography, allowed description of the molecular architecture of the αEB complex. We found that heterodimer dissociation is an energy-independent process that takes place through a disruption of the α-tubulin-β-tubulin interface that is caused by a steric interaction between β-tubulin and the TBCE cytoskeleton-associated protein glycine-rich (CAP-Gly) and leucine-rich repeat (LRR) domains. The protruding arrangement of chaperone ubiquitin-like (UBL) domains in the αEB complex suggests that there is a direct interaction of this complex with the proteasome, thus mediating α-tubulin degradation.
Departamento de Estructura de Macromoléculas, Centro Nacional de Biotecnología (CNB-CSIC), Madrid 28049, Spain.