B. Summary of the sequential involvement of the two DC domains at different stages of MT assembly, characterized by different (bent or straight) tubulin conformations and different nucleotide states. Straight arrows indicate stabilization of tubulin-tubulin contacts. The colour-coded T shapes suggest DC domain-dependent inhibition of structural change: CDC binding between bent tubulin dimers may restrict longitudinal curvature of the assembly in addition to stabilizing the lateral and longitudinal contacts between tubulin dimers, and the subsequent CDC and NDC binding to MT lattice appears to lock tubulin in the lattice-specific straight conformation, preventing MT depolymerization associated with straight-to-bent tubulin transition. 