The solution structure of the N-terminal domain of human tubulin binding cofactor C reveals a platform for tubulin interaction.
Human Tubulin Binding Cofactor C (TBCC) is a post-chaperonin involved in the folding and assembly of α- and β-tubulin monomers leading to the release of productive tubulin heterodimers ready to polymerize into microtubules. In this process it collaborates with other cofactors (TBC's A, B, D, and E) and forms a supercomplex with TBCD, β-tubulin, TBCE and α-tubulin. Here, we demonstrate that TBCC depletion results in multipolar spindles and mitotic failure. Accordingly, TBCC is found at the centrosome and is implicated in bipolar spindle formation. We also determine by NMR the structure of the N-terminal domain of TBCC. The TBCC N-terminal domain adopts a spectrin-like fold topology composed of a left-handed 3-stranded α-helix bundle. Remarkably, the 30-residue N-terminal segment of the TBCC N-terminal domain is flexible and disordered in solution. This unstructured region is involved in the interaction with tubulin. Our data lead us to propose a testable model for TBCC N-terminal domain/tubulin recognition in which the highly charged N-terminus as well as residues from the three helices and the loops interact with the acidic hypervariable regions of tubulin monomers.
Departamento de Química Física Biológica, Instituto de Química Física Rocasolano, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
Ma Flor
MF
Garcia-Mayoral
Raquel
R
Castaño
Monica L
ML
Fanarraga
Juan Carlos
JC
Zabala
Manuel
M
Rico
Marta
M
Bruix
D018385:Centrosome / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000737:chemistry* / Q000378:metabolism*; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012996:Solutions; D014404:Tubulin / Q000737:chemistry / Q000378:metabolism*
D018832:Molecular Chaperones; D012996:Solutions; D014404:Tubulin; C455270:tubulin-specific chaperone C