Abstract
Polymerization under sonication has been developed as a new method to study the rapid polymerization of actin with a large number of elongating sites. The theory proposed assumes that filaments under sonication are maintained at a constant length by the constant input of energy. The data obtained for the reversible polymerization of ADP-actin under sonication have been successfully analyzed according to the proposed model and, therefore, validate the model. The results obtained for the polymerization of ATP-actin under sonication demonstrate the involvement of ATP hydrolysis in the polymerization process. At high actin concentration, polymerization was fast enough, as compared to ATP hydrolysis on the F-actin, to obtain completion of the reversible polymerization of ATP-actin before significant hydrolysis of ATP occurred. A critical concentration of 3 microM was determined as the ratio of the dissociation and association rate constants for the interaction of ATP-actin with the ATP filament ends in 1 mM MgCl2, 0.2 mM ATP. The plot of the rate of elongation of filaments versus actin monomer concentration exhibited an upward deviation at high actin concentration that is consistent with this result. The fact that F-actin at steady state is more stable than the ATP-F-actin polymer at equilibrium suggests that the interaction between ADP-actin and ATP-actin subunits at the end of the ATP-capped filament is much stronger than the interaction between two ATP-actin subunits.
Highlights
Polymerization undersonication has been developed critical Concentration, F-actin in ATP undergoes a transition as a new method to study the rapid polymerization of between the uncappedconformation and the actinwithalargenumber of elongating sites
The classical kinetic analysis of actin polymerization con- of ATP-actin is revealed by the results of polymerization sists in computer fittinofgtheoretical models to experimental under sonication
Analysis of the polymerization curvesobtained cause, in addition to the accurate determination of kinetic at high actin concentrations demonstrates the existence of a parameters, they allow a rapid elimination of oversimplified transient reversiblepolymerization
Summary
Vol 260,No 11,Issue of June 10,pp. 6565-6571,1985 Printed in U.S.A. Polymerization of ADP-Actin and ATP-Actin under Sonication and Characteristics of the ATP- ActinEquilibrium Polymer*. The equilibrium and kinetic parameters for the polymerization of ADP-actin [6, 7] are known, as are the critical concentration of ATP-actin at steady state, the rateconstant for ATP hydrolysis on F-actin [3,4], and theassociation and dissociation rate constants of ATP-actin for the steady-state polymer [3,4, 12]. The issue which we deal with in this paper is the determination of the equilibrium and kinetic parameters for the reversible polymerization of ATP-actin inthe absence for the interactioonf ATP-actin with thAe TP filament of ATP hydrolysis. This can be accomplished provided that ends in 1 mM MgCIZ,0.2 mM ATP. Reaction is associated with it,F-actin polymerized inthe presence of ATP is a steady-statepolymer with a cap of ATP
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
