Lateral bonds between protofilaments:
stabilize the microtubule
limit subunit addition and subtraction to microtubule ends
Microtubules are polarized polymers. The plus end is crowned by β-tubulin and assembles faster.
The minus end is crowned by α-tubulin and assembles slower.
7.3 Microtubules are polar polymers of α- and β- tubulin