D. Actin-binding proteins The structures and functions of cytoskeleton are mainly controlled by its binding proteins ) Monomer-sequestering proteins thymosin and (profilin), Promoting the assembly of mF Bind with actin monomers and prevent them from polymerizing
D. Actin-binding proteins The structures and functions of cytoskeleton are mainly controlled by its binding proteins (1) Monomer-sequestering proteins Bind with actin monomers and prevent them from polymerizing. thymosin and ( profilin) Promoting the assembly of MF
protein binds and keeps actin in ADP-bound form ATP AT ADP site that binds to actin filament protein bound over actin-binding site CAN POLYMERIZE CANNOT POLYMERIZE Figure 16-53 Two possible mechanisms by which an actin monomer-binding protein could inhibit actin polymerization. It is thought that thymosin inhibits actin polymerization in one of these ways
Figure 16-53 Two possible mechanisms by which an actinmonomer-binding protein could inhibit actin polymerization. It is thought that thymosin inhibits actin polymerization in one of these ways
(2) MF-binding proteins End-blocking (capping Ing LOt sequestering Monomers filaments 之。之 Membrane-binding Filament-severing
(2) MF-binding proteins
4 Actin filaments are likewise strongly affected by the binding of accessory proteins along their sides. >Actin filaments in most cells are sta bilized by the binding of tropomyosin, an elongated protein. Which can prevent the filament from interacting with other proteins. > Another important actin filament binding protein, cofilin, present in all eucaryotic cells, which destabilized actin filaments(also called actin depolymerizing factor Cofilin binds along the length of the actin filament, forcing the filament to twist a little more tightly. In addition, cofilin binding cause a large increase in the rate of actin filament treadmilling
❖Actin filaments are likewise strongly affected by the binding of accessory proteins along their sides. ➢Actin filaments in most cells are stabilized by the binding of tropomyosin, an elongated protein. Which can prevent the filament from interacting with other proteins. ➢Another important actin filament binding protein, cofilin, present in all eucaryotic cells, which destabilized actin filaments(also called actin depolymerizing factor). ▪Cofilin binds along the length of the actin filament, forcing the filament to twist a little more tightly. ▪In addition, cofilin binding cause a large increase in the rate of actin filament treadmilling
The modular structures of four actin-cross-linking proteins spectrin ( tetramer (monomer) DL-actinin [dimer) filamin (dimer) The formation of two types of actin filament bundles. >Contractile bundle mediated by a-actinin parallel bundle mediated contractile bundle parallel bundle by fimbrin loose packing allows myosin-lIl tight packing prevents myosin .ll to enter bundle rom entering bundle
The modular structures of four actin-cross-linking proteins The formation of two types of actin filament bundles: ➢Contractile bundle mediated by -actinin ➢parallel bundle mediated by fimbrin