Thiol oxidation of actin produces dimers that enhance the elasticity of the F-actin network.
Slow oxidation of sulfhydryls, forming covalently linked actin dimers and higher oligomers, accounts for increases in the shear elasticity of purified actin observed after aging. Disulfide-bonded actin dimers are incorporated into F-actin during polymerization and generate cross-links between actin filaments. The large gel strength of oxidized actin (>100 Pa for 1 mg/ml) in the absence of cross-linking proteins falls to within the theoretically predicted order of magnitude for uncross-linked actin filament networks (1 Pa) with the addition of sufficient concentrations of reducing agents such as 5 mM dithiothreitol or 10 mM beta-mercaptoethanol. As little as 1 gelsolin/1000 actin subunits also lowers the high storage modulus of oxidized actin. The effects of gelsolin may be both to increase filament number as it severs F-actin and to cover the barbed end of an actin filament, which otherwise might cross-link to the side of another filament via an actin dimer. These new findings may explain why previous studies of actin rheology report a wide range of values when purified actin is polymerized without added regulatory proteins.
Tang
J X
JX
Hematology Division, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA. tang@calvin.bwh.harvard.edu
Janmey
P A
PA
Stossel
T P
TP
Ito
T
T
D000199:Actins / Q000737:chemistry*; D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D003432:Cross-Linking Reagents; D019281:Dimerization; D004548:Elasticity; D005782:Gels; D066298:In Vitro Techniques; D007700:Kinetics; D008956:Models, Chemical; D010084:Oxidation-Reduction; D011487:Protein Conformation; D011817:Rabbits; D012212:Rheology; D013438:Sulfhydryl Compounds / Q000737:chemistry; D014783:Viscosity
D000199:Actins; D003432:Cross-Linking Reagents; D005782:Gels; D013438:Sulfhydryl Compounds