Computer simulations of actin polymerization can explain the barbed-pointed end asymmetry

Computer simulations of actin polymerization were performed to investigate the role of electrostatic interactions in determining polymerization rates. Atomically detailed models of actin monomers and filaments were used in conjunction with a Brownian dynamics method. The simulations were able to rep...

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Bibliographic Details
Published in:Journal of molecular biology 1999-12, Vol.294 (5), p.1181-1189
Main Authors: Sept, David, Elcock, Adrian H, McCammon, J.Andrew
Format: Article
Language:English
Subjects:
Actin Cytoskeleton - metabolism
Actin Cytoskeleton - ultrastructure
Actin Depolymerizing Factors
actin polymerization
Actins - chemistry
Actins - metabolism
Biopolymers
Brownian dynamics
Calcium - metabolism
Computer Simulation
Destrin
Diffusion
diffusion limited
Dimerization
Kinetics
Microfilament Proteins - metabolism
Models, Molecular
Osmolar Concentration
Protein Binding
protein-protein association
Static Electricity
Thermodynamics
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Summary:Computer simulations of actin polymerization were performed to investigate the role of electrostatic interactions in determining polymerization rates. Atomically detailed models of actin monomers and filaments were used in conjunction with a Brownian dynamics method. The simulations were able to reproduce the measured barbed end association rates over a range of ionic strengths and predicted a slower growing pointed end, in agreement with experiment. Similar simulations neglecting electrostatic interactions indicate that configurational and entropic factors may actually favor polymerization at the pointed end, but electrostatic interactions remove this trend. This result would indicate that polymerization at the pointed end is not only limited by diffusion, but faces electrostatic forces that oppose binding. The binding of the actin depolymerizing factor (ADF) and G-actin complex to the end of a filament was also simulated. In this case, electrostatic steering effects lead to an increase in the simulated association rate. Together, the results indicate that simulations provide a realistic description of both polymerization and the binding of more complex structures to actin filaments.
ISSN:0022-2836
1089-8638
DOI:10.1006/jmbi.1999.3332