CALMODULIN-STIMULATED ATPASE OF MAIZE CELLS - FUNCTIONAL RECONSTITUTION, MONOCLONAL-ANTIBODIES AND SUBCELLULAR-LOCALIZATION

Microsomal calmodulin-stimulated ATPase (CaM-ATPase) was purified from dark-grown maize shoots by affinity chromatography and functionally r econstituted into phosphatidylcholine vesicles by detergent dialysis. the resultant proteoliposomes showed CaM-stimulated ATP hydrolysis and CaM-stimulated ATP-dependent calcium uptake, indicating that the CaM- ATPase is a calcium pump. Microsomal membranes prepared from dark-grow n maize shoots were fractionated in continuous sucrose gradients. Calc ium transport was observed in plasma membrane and intracellular membra ne fractions, but the bulk of the calmodulin-stimulated activity was f ound to be associated with intracellular membranes. Five monoclonal an tibodies were raised to affinity purified CaM-ATPase. Immunocytochemic al data from roots suggested that the CaM-ATPase might be associated w ith membranes involved in the function of the mitotic apparatus in mer istematic tissue.