Partial Purification and Characterization of An ATPase in Mung Bean Hypocotyl Plasma Membrane: Suggestion for A New Type of Higher Plant Plasma Membrane ATPase

A vanadate-sensitive and nitrate-resistant ATPase was solubilizedwith Zwittergent 3–14 from a highly purified plasma membranefraction of mung bean hypocotyls and partially purified by glyceroldensity gradient centrifugation and phenyl-Sepharose columnchromatography. Either phosphatidylcholine or phosphatidylserinein addition to Mg^{2 +} was required for the enzyme activity, whereasK⁺, phosphatidylethanolamine and lysophosphatidylcholine hadno effect on the activity. The purified enzyme preparation containedtwo major polypeptides with molecular masses of 67 and 55 kDaas analyzed by SDS-polyacrylamide gel electrophoresis. Whenthe plasma membrane fraction was incubated with -³²P]ATP, a45-70-kDa polypeptide(s) was labeled, and the label could berapidly chased with cold ATP. When the fraction was incubatedwith ¹⁴C]N,N'-dicyclohexylcarbodiimide, an inhibitor for theATPase, a 15-20-kDa polypeptide was labeled. We propose thatthe enzyme is a new type of higher plant plasma membrane ATP-aseand is composed of 67- and 55-kDa subunits and probably alsoa 15-20-kDa subunit. ¹Present address: Takarazuka Institute, Sumitomo Chemical IndustriesLtd., Takatsukasa, Takarazuka, Hyogo 665, Japan (Received September 2, 1987; Accepted May 20, 1988)