Model of KinI core function. Purple=α-tubulin, light blue=β-tubulin, yellow=KinI catalytic core, red=loop 2, green=region of KinI that attaches to β-tubulin (possibly N-terminal ‘neck', L12, L8): (1) When KinI recognizes and binds a tubulin dimer at the end of an MT, L2 binds to α-tubulin, and another KinI element, such as L12 and/or the neck, binds to β-tubulin. The majority of the KinI core binds at the intradimer interface. (2) When ATP binds to KinI, it induces a conformational change in the catalytic core that pulls the tubulins at the L2 and ‘neck' attachments and pushes in at the intradimer interface, curving the dimer. (3) With KinI in this new tubulin-binding conformation, ATP hydrolysis is stimulated. (4) ATP hydrolysis weakens the tubulin dimer's connection to the MT, releasing the dimer–KinI complex. It also weakens KinI binding to tubulin, freeing KinI into solution for rebinding and continued depolymerization of MT.