Electrostatic balance between global repulsion and local attraction in reentrant polymerization of actin

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4 Citations (Scopus)

Abstract

Actin polymerization depends on the salt concentration, exhibiting a reentrant behavior: the polymerization is promoted by increasing KCl concentration up to 100 mM, and then depressed by further increase above 100 mM. We here investigated the physical mechanism of this reentrant behavior by calculating the polymerization energy, defined by the electrostatic energy change upon binding of an actin subunit to a filament, using an implicit solvent model based on the Poisson-Boltzmann (PB) equation. We found that the polymerization energy as a function of the salt concentration shows a non-monotonic reentrant-like behavior, with the minimum at about 100 mM (1:1 salt). By separately examining the salt concentration effect on the global electrostatic repulsion between the like-charged subunits and that on the local electrostatic attraction between the inter-subunit ionic-bond-forming residues in the filament, we clarified that the reentrant behavior is caused by the change in the balance between the two opposing electrostatic interactions. Our study showed that the non-specific nature of counterions, as described in the mean-field theory, plays an important role in the actin polymerization. We also discussed the endothermic nature of the actin polymerization and mentioned the effect of ATP hydrolysis on the G-F transformation, indicating that the electrostatic interaction is widely and intricately involved in the actin dynamics.

Original languageEnglish
Pages (from-to)504-511
Number of pages8
JournalCytoskeleton
Volume74
Issue number12
DOIs
Publication statusPublished - 2017 Dec

Keywords

  • Debye-Hückel formula
  • G-F transformation
  • generalized Born model
  • reentrant transition
  • salt concentration dependence

ASJC Scopus subject areas

  • Structural Biology
  • Cell Biology

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