Characterization of ATPases Associated with Various Cellular Membranes Isolated from Etiolated Hypocotyls ofVigna radiata(L.) Wilczek1

摘要

Cellular membrane fractions, including endoplasmic reticum (ER), Golgi-enriched membrane, plasma membrane and tonoplasts, were isolated fromVigna radiataseedlings. Each of these membrane fractions was associated with specific ATPases which were highly dependent on Mg2+. ATPases of ER, Golgi-enriched membrane and plasma membrane were sensitive to vanadate but the tonoplast ATPase was not. ATPases were mostly dependent on Cl1, but a slight stimulation by K+was observed in the case of ATPases of Golgi-enriched membrane and plasma membrane. KNO3inhibited tonoplast ATPase but stimulated the other ATPases. ER ATPase can be distinguished from other ATPases by the following characteristics: specific inhibition by KNO2and Triton X-100, stimulation by low concentrations of diethylstilbestrol and 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid, and high sensitivity to heat. The ATPases showed typical Michaelis-Menten kinetics and had Kmvalues of 0.5 to 0.6 ITIM Mg2+-ATP for ER, Golgienriched-membrane and tonoplast ATPases, and 2.27 msi Mg2+-ATP for plasma membrane ATPase. ATPases of Golgi-enriched membranes and plasma membranes had similar properties, but they were still distinguishable by the differences in theirKmvalues and their responses to Triton X-100. Based on these results, it is postulated that each cellular membrane is associated with a specific ATPase in cells ofV. radi