Figure 9. A revised scheme for tubulin factors and Arl2 as a chaperone multi-subunit machine in regulating soluble αβ-tubulin.
(A) Revised paradigm, based on data from this study for tubulin cofactors and Arl2 as a multi-subunit chaperone that cycles to regulate soluble αβ-tubulin through GTP hydrolysis catalytic cycles, while providing sites for α and β-tubulin dissociation for biogenesis and degradation. Through this model, dual GTP hydrolyses in Arl2 and possibly in αβ-tubulin sequentially induce tubulin dimer dissociation without release. We suggest that αβ-tubulin is reassembled and then released. (B) An overall model for how TBC-DEG/TBCC activity cycles may regulate slowly decaying tubulin by binding along the TBC-DEG platform, recruiting TBCC, and then dissociating α and β-tubulin from each other, without dissociation from the TBC-DEG/TBCC platform.