Elsevier

Biophysical Chemistry

Volume 3, Issue 3, July 1975, Pages 215-225
Biophysical Chemistry

Kinetics of the cooperative association of actin to actin filament

https://doi.org/10.1016/0301-4622(75)80013-5Get rights and content

Abstract

The cooperative formation ofactin filaments from monomers was followed by light scattering and electron microscopy. The results are well described by a simple model mechanism in which the growth and destruction of filaments occurs by stepwise addition or dissociation of protoniers. All steps except the dimerisation step are assumed to have identical rate constants. These were found to be 5 × 103 M−1 sec−1 and 3 × 10−2 sec−1 for the association and dissociation, respectively (at pH 7.5 and in the presence of 10−3 M calcium chloride. The equilibrium constant of elongation as obtained from the critical concentration is 1.7 × 105 M−1. The corresponding equilibrium constant of dimerisation is about 10 million times smaller (cooperativity parameter σ = 2 × 10−7). This makes the nucleation extremely difficult and cooperativity very high. A best (it of the model to the experimental data is achieved when the destruction of a dimer is much faster than the addition of a third protomer (fast monomer-dimer pre-equilibrium). The size of the nucleus from which propagation becomes faster than dissociation is 3.

References (27)

  • F. Oosawa et al.

    J. Mol. Biol.

    (1962)
  • S. Asakura

    J. Mol. Biol.

    (1968)
  • M. Rees et al.

    J. Biol. Chem.

    (1967)
  • H. Huxley et al.

    J. Mol. Biol.

    (1960)
  • F.B. Straub et al.

    Biochim. Biophys. Acta

    (1950)
  • D. Pörschke et al.

    J. Mol. Biol.

    (1971)
  • F. Oosawa

    J. Theor. Biol.

    (1970)
  • S. Asakura

    Advan. Biophys.

    (1970)
  • C.J. Lusty et al.

    Biochemistry

    (1969)
  • A. Gomall et al.

    J. Biol. Chem.

    (1949)
  • M. Elzinga et al.

    Proc. Nat. Acad. Sci. USA

    (1973)
  • J. Hanson et al.

    J. Mol. Biol.

    (1973)
  • C.C. Selby et al.

    J. Biophys. Biochem. Cytol.

    (1956)
  • Cited by (190)

    • Actin Assembly Dynamics and Its Regulation in Motile and Morphogenetic Processes

      2022, Encyclopedia of Cell Biology: Volume 1-6, Second Edition
    • Mechanism of actin filament nucleation

      2021, Biophysical Journal
      Citation Excerpt :

      Cooper et al. (7) separated each nucleation step by using a model that built the filament nucleus by sequential addition of monomers with equivalent association and dissociation rate constants. Given very limited computing power at the time, Cooper et al. (7) made the same steady-state assumption as Wegner and Engel (3). They assumed a dissociation rate constant of 500 s−1 for each nucleation step, a value that produced a rapid equilibrium.

    • The role of annealing and fragmentation in human tau aggregation dynamics

      2019, Journal of Biological Chemistry
      Citation Excerpt :

      These data demonstrate that 2N4R tau annealing rates are robust and measurable. To rigorously quantify the contribution of annealing and other secondary processes to tau aggregation kinetics, 2N4R tau aggregation time series were fit by an equilibrium nucleation–elongation scheme (8, 37) modified to include secondary events, including secondary nucleation, fragmentation, and end-to-end annealing (Fig. 1). The nucleation component of the primary pathway was constrained to a cluster size of 2 on the basis of previous rate measurements (8).

    View all citing articles on Scopus
    View full text