Issue 13, 2015

Cosolvent and crowding effects on the polymerization kinetics of actin

Abstract

We studied the effects of kosmotropic and chaotropic cosolvents, trimethylamine-N-oxide (TMAO) and urea, as well as crowding agents (dextran) on the polymerization reaction of actin. Time-lapse fluorescence intensity and anisotropy experiments were carried out to yield information about the kinetics of the polymerization process. To also quantitatively describe the effects, cosolvents and crowding impose on the underlying rate constants of the G-to-F-transformation, an integrative stochastic simulation model was applied. Drastic and diverse changes in the lag phase and association rates as well as the critical actin concentration were observed under different solvent conditions. The association rate constant is drastically increased by TMAO but decreased by urea. In mixtures of these osmolytes, TMAO counteracts not only the deleterious effect of urea on protein structure and stability, but also on the protein–protein interactions in the course of actin polymerization. Owing to the excluded volume effect, cell-like macromolecular crowding conditions increase the nucleation and association rates by one order of magnitude. Our results clearly reveal the pronounced sensitivity of the actin polymerization reaction to changes in cosolvent conditions and the presence of macromolecular crowding, and suggest that such effects should be taken into account in any discussion of the actin polymerization reaction in vivo.

Graphical abstract: Cosolvent and crowding effects on the polymerization kinetics of actin

Article information

Article type
Paper
Submitted
30 Sep 2014
Accepted
30 Okt 2014
First published
07 Nov 2014

Phys. Chem. Chem. Phys., 2015,17, 8330-8337

Author version available

Cosolvent and crowding effects on the polymerization kinetics of actin

C. Rosin, P. H. Schummel and R. Winter, Phys. Chem. Chem. Phys., 2015, 17, 8330 DOI: 10.1039/C4CP04431B

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