Polymerization actin

Zigmond, 1988). The ATP-hydrolysis that accompanies actin polymerization, ATP —> ADP + Pj, and the subsequent release of the cleaved phosphate (Pj) are believed to act as a clock (Pollard et ah, 1992 Allen et ah, 1996), altering in a time-dependent manner the mechanical properties of the filament and its propensity to depolymerize. Molecular dynamics simulations suggested a so-called back door mechanism for the hydrolysis reaction ATP ADP - - Pj in which ATP enters the actin from one side, ADP leaves from the same side, but Pj leaves from the opposite side, the back door (Wriggers and Schulten, 1997b). This hypothesis can explain the effect of the toxin phalloidin which blocks the exit of the putative back door pathway and, thereby, delays Pi release as observed experimentally (Dancker and Hess, 1990). 

Dancker and Hess, 1990] Dancker, P., and Hess, L. Phalloidin reduces the release of inorganic phosphate during actin polymerization. Biochira. Biophys. Acta. 1035 (1990) 197-200... 

Theriot et al., 1992] Theriot, J. A., Mitchison, T. J., Tilney, L. G., and Portnoi, D. A. The rate of actin-based motility of intracellular Listeria monocytogenes equals the rate of actin polymerization. Nature. 357 (1992) 257-260... 

Another subfamily of ADP-iibosylating toxins modifies G-actin (at Argl77), thereby inhibiting actin polymerization. Members of this family are, for example, C. botulinum C2 toxin and Clostridium perfringens iota toxin. These toxins are binary in structure. They consist of an enzyme component and a separate binding component, which is structurally related to the binding component of anthrax toxin [3]. 

C. botulinum C2-toxin and related toxins Actin ADP-ribosylation Inhibition of actin polymerization... 

In contrast, jasplakinolide, a cyclodepsipeptide from the marine sponge Jaspis johnstoni, rapidly penetrates the cell membrane. It competes with phalloidin for F-actin binding and has a dissociation constant of approximately 15 nM. It induces actin polymerization and stabilizes pre-existing actin filaments. Dolastatin 11, a depsipeptide from the mollusk Dolabella auricu-laria, induces F-actin polymerization. Its binding site differs from that of phalloidin or jasplakinolide. 

SARA is a scaffolding protein that regulates the subcellular localization of inactivated R-Smads, potentially scaffolding the TGF-P receptor kinase to the Smad 2 substrate. Filamins are a family of actin polymerization proteins that also form scaffolds for a range of signaling proteins including SAP kinases such as MKK-4, small GTPases Rho and Ras, as well as Smad 2 and Smad 5. 

Nonmuscle Actin-Binding Proteins Drugs Affecting Actin Polymerization Patterns of Arrangement of Actin Filaments in Animal Cells Three-Dimensional Networks The Microtrabecular Lattice... 

Blood platelets are key players in the blood-clotting mechanism. These tiny fragments of cytoplasm are shed into the circulation from the surface of megakaryocytes located in the bone marrow. When the lining of a blood vessel is injured, activated platelets release clotting factors, adhere to each other and to damaged surfaces, and send out numerous filopodia. The shape changes that occur in activated platelets are the result of actin polymerization. Before activation, there are no microfilaments because profilin binds to G-actin and prevents its polymerization. After activation, profilin dissociates from G-actin, and bundles and networks of F-actin filaments rapidly appear within the platelet. 

Actin Polymerization Regulation by Divalent Metal Ion and Nucleotide Bindings ATP Hydrolysis and Actin Binding Proteins... 

ATP HYDROLYSIS LINKED TO ACTIN POLYMERIZATION PERTURBS THE THERMODYNAMICS OF REVERSIBLE POLYMERIZATION... 

The fact that the concentration of G-actin at steady-state in the presence of ATP varies with the number of filaments may have some biological significance indeed, in cells, large pools of G-ADP-actin may accumulate in regions where a large number of short filaments exist. This behavior is the direct consequence of two combined features of actin polymerization namely, the hydrolysis of ATP, and the relatively slow rate of ATP exchange for ADP on G-actin. 

The Locomotion of Amoeba The Locomotion of Fibroblastic Cell Types The Locomotion of Leukocytes The Behavior of Locomoting Cells The Role of the Cytoskeleton in Cell Locomotion The Microtubule-Based Cytoskeleton The Intermediate Filament-Based Cytoskeleton The Microfilament-Based Cytoskeleton The Organization of Microfilaments in Cells Microfilament Dynamics and Cell Locomotion Sites of Lamellar Protrusion May Be Determined by the Nucleation of Actin Polymerization... 

Sites of Lamellar Protrusion May Be Determined by the Nucleation of Actin Polymerization... 

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