Dr Mah Jabeen Muneera Assistant Professor Department of Anatomy KEMU

Importance Microtubules Microfilaments Intermediate filaments

shape: hollow cylinders Diameter: 20-25nm Basic protein subunit: Dimers of α and β tubulin

polarity: _ (minus) end is non growing and + end is the growing end Dynamic instability: Polymerization and depolymerization Stable microtubules in cilia and flagella

Immotile cilia syndrome Mutations in dyenin protein Respiratory tract infections and infertility

Centrosome: Centrioles and pericentriolar material Centrioles provide basal bodies for cilia and flagella

An amorphous protein matrix with an abundance of tubulin rings. Each tubulin ring serves as the nucleation site for the growth of a single microtubule. Minus (–) end of the microtubule remains attached to the MTOC, and the plus end represents the growing end directed toward the plasma membrane.

In the absence of centrioles, astral microtubules fail to develop, causing errors in mitotic spindle formation.

Colchicine Prevents polymerization 1.It binds specifically to tubulin 2.Tubulin-colchicine complex binds to microtubules 3. TC complex prevents the addition of more tubulin in the plus extremity used to prepare karyotype treatment of acute stages of gout Karyotype

Taxol – accelerates polymerization and prevent depolymerization thus stabilizing microtubules - cancer chemotherapy Vinblastine and Vincristine- accelerates depolymerization and form paracrystalline arrays - cancer chemotherapy

MAPs 1,2,3,4 stabilize microtubules Motor proteins- dyneins and kinesins- required for organelle movement