Cytoskeleton II Chapter 16

Tubulin heterodimer is the microtubule subunit

Microtubule structure

Growing and shrinking microtubules

Growing and shrinking microtubules

Structure of actin

Actin binds to many different proteins

Intermediate filaments

Model of intermediate filament structure

Model of intermediate filaments

Intermediate filaments can withstand high levels of deforming force

Keratin filaments in an epithelial cell

Blistering of the skin caused by a mutant keratin gene Normal skin

Blistering of the skin caused by a mutant keratin gene Skin with mutated keratin gene

Blistering of the skin caused by a mutant keratin gene Cells rupture between the nucleus and the hemi- desmosomes

Polymerization of tubulin is nucleated by the γ-tubulin ring

Electron micrograph of purified γ-tubulin complexes

Single microtubules nucleated from the γ-tubulin ring

The centrosome is the major microtubule organizing center of animal cells and contain γ-tubulin ring complexes

Centriole surrounded by centrosome matrix

figure 09-08a.jpg

figure 09-08a.jpg

figure 09-09.jpg Figure 9.9 Figure 9.9 spindle

figure 09-08b.jpg

Leading edge of cell nucleates actin filaments all actin filaments Newly formed actin filaments

Model for actin filament nucleation by ARP complex

ARP complex nucleates more efficiently when bound to preexisting actin filament

Electron micrograph of branched actin filaments

Thymosin inhibition

Profilin recruitment

Stathmin sequesters free tubulin

Monomer concentration and capping protein determine growth or shrinkage rate

Stabilization and destabilization of microtubules

Capping proteins direct microtubules to specific locations in the cell