Plant and Cell Physiology, 2001, Vol. 42, No. 5 531-537
© 2001 Oxford University Press
Regulation of the H+ Pump Activity in the Plasma Membrane of Internally Perfused Chara corallina
1 National Institute for Physiological Sciences, Myodaiji, Okazaki, 444-8585 Japan 2 Department of Biological Sciences, Faculty of Life and Environmental Science, Shimane University, Matsue, Shimane, 690-0823 Japan
The role of cytoplasm for the maintenance of the H+ pump activity in Chara corallina internodal cells was examined by the intracellular perfusion technique. Cytoplasm-rich and -poor states were obtained by changing the perfusion time, short-term (less than 2 min) and long-term (more than 5 min), respectively. A large portion of cytoplasm was left by short-term perfusion but most of the cytoplasm was removed by long-term perfusion. The activities of the H+ pump of these two different conditions were examined by measuring current-voltage relation (I-V curve) and conductance-voltage relation (G-V curve) under voltage clamp conditions. The H+ pump conductance decreased to 37%, 9% and zero by short-term, long-term and hexokinase perfusion, respectively, whereas the passive channel conductance decreased to 71%, 39% and 73% by short-term, long-term and hexokinase perfusion, respectively. On the other hand, the electromotive-force of the H+ pump (~ –260 mV) and the passive channel (~ –130 mV) were not affected by either short- or long-term perfusion. It is indicated that the cytoplasm plays an essential role to regulate the activity of both the H+ pump and the passive channel together with ATP.
3 Corresponding author: E-mail, tsutsui@nips.ac.jp; Fax, +81-564-52-7913; Phone, +81-564-55-7832.