Actin and IFs Flashcards
Intermediate filaments
rope like fibers, made of intermediate filament proteins, large and heterogenous family
forms the nuclear lamina
Span across the cyto for strength
span from epithelial cell to epithelial cell to stapilize epithelium
non polarized tetramer, high tensile filaments without motor proteins (phosphorylation and de phos lead to assembly and disassembly) vimentin and desmin
ends are essential for filament assembly
skin cells with defective keratin are stress susceptible-> blistering disease
Actin filament
highly conserved for the cytoskeleton, actin binds to itself (alpha beta and gamma subunits)
regulation is important for cell structure
Clinical: muscular disease, bacteria, drugs used by researchers (cytochalasin and phalloidin)
G actin monomers-> rapidly degraded F actin (polymerized)-> have ATP bound
Subunit binding and ATP hydrolysis are not coupled processes
treadmilling of actin
critical concentration free subunit concentration at which on and off rates are equal
minus end throws off the actin before the plus end
Accessory proteins regulate the rate of polymerzation
Actin binding proteins
Regulators: tropomyosin, capping protein, ARPs) Thymosin inhibition (keeps ATP), proflin (keeps ADP)
Severing (cofilin gelsolin)
Cross linking (spectrin Motor: mysoin types 1 and 2
Actin Dendritic Array treadmilling at the protruding edge
actin polymerization forces push the membrane forward
Arp is activated by W, and binds to F actin to nucleate growth, capping inhibits, coglin severs G actin is funneled
W-A syndrone defective cell migration
bacteria can hijack actin and move the cell
Orthogonal crosslinking of actin microfilaments
Gel forming proteins hold actin at large angles to create a gel
Phalloidin and cytochalasin
Phalloidins stabilize F actin and lock together
cytochalasin depolymerizes by binding to plus ends
