PHALLOIDIN BINDS AND STABILIZES PEA ROOT ACTIN

Previous reports about phalloidin binding to plant actins have been indirect. We present here evidence showing that phalloidin does bind and stabilize filaments of actin extracted from pea roots. Criteria for the presence of actin included stabilization as a polymer in the presence of phalloidin, cross-reaction with antibody against chicken actin, affinity binding to DNase I, and ability to be decorated by the S1 fragment of rabbit muscle myosin. Phalloidin was able to stabilize polymers in pea root extracts against dissociation during SDS gel electrophoresis, and these polymers were shown to be composed exclusively of actin. Pea root actin isolated by affinity chromatography on a DNase I column was incubated with rhodamine phalloidin and electrophoresed on a native gel. The rhodamine fluorescence remained with the stabilized filaments, indicating clearly that phalloidin does bind to actin from a plant source.