The Isolation of Actin from Pea Roots by DNase I Affinity Chromatography

Native actin can be isolated from pea (Pisum sativum L.) roots by DNase I affinity chromatography, but the resulting yields and quality of actin are variable. By use of two assays for actin, a DNase I inhibition assay and a gel scanning assay, we identified several factors that increased actin yield. ATP is required for the actin in crude pea root extracts to bind to immobilized DNase I. Low amounts of ATP are hydrolyzed rapidly by an endogenous ATPase in the extract, and the actin then irreversibly loses the ability to bind to DNase I. High ATP concentrations (5-10 mm) or inhibition of the ATPase (with 10 mm pyrophosphate) are required for pea actin to retain DNase I binding ability. When adequate amounts of ATP are present, actin binding from the extract is further enhanced by basic pH, formamide, and soluble polyvinyl-pyrrolidone. Once actin is bound to the DNase I-agarose and washed free of extract, high ATP concentrations are not required to keep actin bound. Actin eluted from the DNase I-agarose with formamide retained its ability to polymerize into filaments with the addition of KCl and Mg(2+). The advantages and disadvantages of this procedure and its application to other plant materials are discussed.