PURIFICATION OF AN ACTIN-BINDING PROTEIN COMPOSED OF 115-KDA POLYPEPTIDE FROM POLLEN TUBES OF LILY

From lily pollen tubes, an actin-binding protein composed of 115-kDa p olypeptide was purified sequentially by co-precipitation method with F -actin, hydroxylapatite column, gel filtration column and DE-52 ion ex change column chromatography, This component displayed a tendency to a ggregate in solutions of low ionic strength, indicating a hydrophilic characteristic. Under physiological ionic conditions, this component b ound to F-actin in an actin concentration-dependent was saturable mann er. Binding of this component to F-actin was independent of ATP and Ca 2+-concentrations. Fluorescent microscopy revealed that F-actin labele d with rhodamine-phalloidin showed bundling in the presence of this co mponent. Judging from the lack of antibody cross-reactivity, this comp onent does not seem to be related to cr-actinin of skeletal muscle and plant 135-kDa actin-bundling protein. Therefore, this component is th e F-actin binding protein, which has not been identified thus far in p lant cells. (C) 1998 Academic Press.