Fig. 7. A model for the mechanism of AtMAP65-1 regulation. (A) Diagrams of the secondary structure prediction and charts of charge distribution for anaphase spindle elongation protein 1 (ASE1), AtMAP65-1, PRC1, Feo and spindle defective 1 (SPD1). Blue colour represents helices, red represents ß strand and violet represents coiled coil. (B) Scheme for the interaction between AtMAP65-1 and microtubules. Two microtubule-interacting sites on AtMAP65-1 are needed for normal function. One site is not affected by phosphorylation and is not coloured, the second site is normally alkaline (shown is blue). The alkaline region binds to the acidic C-terminal region of tubulin (shown in red). After phosphorylation the charge of the second microtubule-interacting site changes to acidic (shown in red). This weakens the binding of AtMAP65-1 to microtubules.