Keratin filaments 2. Vimentein and vimentin-related filaments 3. Microtubules Tubulin Exists as a heterodimer of two globular proteins, alpha and beta tubulin. A microtubule is a cylindrical structure with a hollow core, formed by 13 subunits of tubulin. 16-21 Antimitotic drugs, colchicine, nocadozole, colcemid Taxol , binds tightly to microtubules and stabilizes them.
Centrosomes are the primary site of nucleation of microtubules in animal cells.
As the tubulin subunits polymerize they can be covalently modified by acetylation of a lysine and a detyrosination of a tyrosine residue from the c-terminus. MAPs bind to microtubules and mediate interaction with other cell components. 55-60 kD. MAPs have two domains, one binds to microtubules and the other to cell components. MAPs speed up nucleation. MAPs stabilize microtubules by inhibiting the dissociation of tubulin from microtubules.