Microtubules and Cytoskeleton

What are the three types of cytoskeletal filaments?

microtubules

Primary function of microtubules

structure

Primary function of actin filaments

contractility

Primary function of intermediate filaments

mechanical strength

Microtubules vs actin structure

microtubules=hollow tubes

Microtubule composition

α-tubulin and β-tubulin heterodimers

Which tubulin hydrolyzes GTP?

β-tubulin (α-tubulin binds but cannot hydrolyze)

Protofilament number in microtubules

13

Microtubule polarity

plus end (β-tubulin exposed)

Dynamic instability definition

alternating growth/shrinkage at plus end

GTP cap function

stabilizes microtubule when GTP-bound β-tubulin at plus end

What triggers catastrophe?

GDP-bound β-tubulin exposed at plus end

Microtubule-affecting drugs

Taxol (stabilizes)

Two main microtubule motor proteins

kinesin

Kinesin movement direction

plus-end directed (mostly)

Dynein movement direction

minus-end directed

Motor protein power source

ATP hydrolysis

Motor protein cargo

vesicles

KIF5B knockout effect

mitochondria cluster instead of distributing

Main MTOC in animal cells

centrosome

Centrosome core structure

pair of centrioles

Microtubule nucleation

γ-tubulin rings in pericentriolar material

Centriole structure

9 triplet microtubules

Secretory cell microtubule arrangement

minus ends at Golgi

Cilia/flagella structure name

"9+2 array"

9+2 array components

9 outer doublet microtubules + 2 central singlets

Cilia/flagella motor protein

dynein

Bending mechanism

dynein walks on adjacent doublet

Basal body function

nucleates cilia/flagella (modified centriole)

Anterograde IFT transport

kinesin-2

Retrograde IFT transport

cytoplasmic dynein

Taxol mechanism

stabilizes GDP-bound microtubules

Colchicine mechanism

blocks tubulin polymerization

Taxol cancer treatment rationale

freezes mitotic spindle

Neuronal transport speed

5 μm/sec = 0.4 m/day

Kinesin proof experiment

mitochondria clustering in KIF5B knockout