NPA BINDING-ACTIVITY IS PERIPHERAL TO THE PLASMA-MEMBRANE AND IS ASSOCIATED WITH THE CYTOSKELETON

N-1-Naphthylphthalamic acid (NPA) binding activity is released into th e supernatant when plasma membranes are subjected to high-salt treatme nt, indicating that this activity is peripherally associated with the membrane. Extraction of plasma membrane vesicles with Triton X-100 res ulted ire retention of NPA binding activity in the detergent-insoluble cytoskeletal pellet. Treatment of this pellet with KI released NPA bi nding activity, actin, and a-tubulin. Dialysis to remove KI led to the repolymerization of cytoskeletal elements and movement of NPA binding activity into an insoluble cytoskeletal pellet. NPA binding activity partitioned into the detergent-insoluble cytoskeletal pellet obtained from both zucchini and maize membranes and was released from these pel lets by KI treatment. Treatment of a cytoskeletal pellet with cytochal asin B doubled NPA binding activity in the resulting supernatant. Toge ther, these experiments indicate that NPA binding activity is peripher ally associated with the plasma membrane and interacts with the cytosk eleton in vitro.