Polymorphism of F-Actin Assembly. 1. A Quantitative Phase Diagram of F-Actin

Publisher Website
Google Scholar
Abstract
We have made the first quantitative phase diagram of actin filament (F-actin) assembly represented by the concentration of F-actin and the χ parameter which characterizes solvent−solute interaction energy. We manipulated the χ value of F-actin by adding a high molecular weight poly(ethylene glycol) with average molecular weight 6000 (PEG 6K). The preferential exclusion of PEG 6K from the region adjacent to F-actin increases the χ value of F-actin. We quantified the PEG 6K-induced increase of the χ value through analysis of the PEG-induced solubility change of protein. The phase diagram shows that F-actin changes its assembly structure from isotropic disordered distribution to anisotropic ordered phase of a lyotropic liquid crystalline with an increase in the concentration and to concentrated anisotropic ordered phase of a crystalline-like bundle with a small increase in χ, respectively, in the physiological concentration range. The formation of the crystalline-like bundle suggests that some specific force may act between F-actin. The present results demonstrate that F-actin can take various assembly structures as observed in cytoplasm by itself, indicating that the versatility of F-actin assembly in cytoplasm may be based on the thermodynamic properties of F-actin as a rod-like molecule.

This publication has 8 references indexed in Scilit: