Proteine und Kapitel 17

-Protein that binds to G-Actin

-opens cleft and enhances loss of ADP

-ATP can then bind to G-Actin

=> ensures a constant supply of ATP-Actin

-Binds to 2 ADP-actin subunits within F-Actin filaments

-induces small change in twist

=> destabilizes filament and breaking it, creating more - ends

-binds to ATP-G-actin and inhibits its addition to either end of the filament

-free actin and free thymosin-beta 4 are in equillibrium with bound actin-thymosin-beta4

-acts as a buffer for unpolymerized actin, making it available when needed

-binds to the + end of microfilaments, inhibiting any assembly or disassembly

-controlled by

-a phospholipid (inhibitory)

-other regulatory proteins which bind the + end (blocking CapZ binding)

-inhibits assembly or disassembly at the - end of microfilaments

-works with tropomyosin to stabilize

-caps + ends of microfilaments

-regulated by Ca2+ concentration

-binds to the side of actin filaments and inserts itself

-breaks existing filament, then capping the + end

-binds to the + end of microfilaments

-one subunit ist rich in proline residues, recruiting profilin

-Formin allows rapid addition of actin subunits to the + end by rocking between the two actin subunits at the end

-also hinders + end capping proteins from binding

=> enhances long, straight actin filaments

-nucleates branched filament assebly

-needs to be activated by nucleation promoting factor NPF

-in active form binds to the side of existing microfilaments inducing a new + end at a 70° angle

nucleation promoting factor

-WASp

-activated at the plasma membrane

-activation needs 2 signals (coincidence detection)

-WAVE

-activation needs 2 signals (coincidence detection)

-ActA

-mimics NPF

-surface protein of Listeria

-

intracellular parasite

-rapid movement trough the cell is powered by actin polymerization (comet tail)

-surface protein ActA which mimics a NPF

-ATP-G-actin, Arp2/3 complex, CapZ and cofilin are sufficient

Cytochalasin

-depolymerizes actin filaments by binding the + end of f-actin, blocking addition of subunits

Lantrunculin

-binds and groups g-actin inhibiting it from adding to a filament end

=> the rate actin based structures disappear are normal rate of turnover

Jasplakinolide

-lowers critical consentration by binding and stabilizing actin dimers

Phalloidin

-binds existing actin filaments, preventing depolymerization