[Mimosa pudica adenosine triphosphatase]

The morphological structure (pulvinus P1, P2 and P3) directly involved in the seismonastic movements of the Mimosa pudica leaf have been used to isolate: 1) "soluble" ATPase, loosely bound to pulvinus structures; 2) Ca, Mg-dependent ATPase, which is tightly bound to pulvinus structures and is extracted by a saline solution of high ionic strength, used to isolate actomyosin from muscles and non-muscle motile cells; 3) ATPase bound to the pulvinus membrane structures, which is solubilized by the detergents, e. g. Triton X-100 and Tween-80, and is similar to membrane ATPase. Physico-chemical and kinetic studies of the APSases have shown that Ca,Mg-ATPase is similar to the ATPases from muscle and non-muscle motile cells in a number of characteristics, e. g. solubility in saline solution of high ionic strength, aggregability in a solution of lower ionic strength, activation by bivalent metal ions, pH-optimum, specificity for substrates, etc. The protein composition of the ATPases has been determined by gel-electrophoresis in polyacrylamide gel. The molecular weight of purified Ca,Mg-ATPase from Mimosa pudica pulvinus is found to be 139 000. The role of ATPases in seismonastic movements of the Mimosa pudica leaf is discussed.