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Updated: Oct 23, 2026

Actin Co-Sedimentation Assay; for the Analysis of Protein Binding to F-Actin
Published on: March 27, 2008
Effect of erythrocyte spectrin on actin self-association
1Department of Biochemistry, University of Sydney, N.S.W.
Abstract:
The polymerization of pyrene-labelled skeletal muscle actin has been monitored in the presence of chromatographically purified spectrin dimers and tetramers. A small but consistent effect of spectrin binding on the critical concentration was observed for actin polymerized in the presence of 1 mM MgCl2. These data were analysed using the principle of linked functions. Spectrin binds exclusively to the filamentous form of actin, and thereby stabilizes F-actin with respect to the G-form. The decrease in the critical concentration for actin polymerization, in the presence of spectrin, has been shown to be consistent with an equilibrium constant for the binding of spectrin to individual promoters within F-actin of approximately 8 X 10(5) M-1 at 23 degrees C, and an ionic strength of 7 mM.
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