Regulation of the H+ pump activity in the plasma membrane of internally perfused Chara corallina.
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 (approximately -260 mV) and the passive channel (approximately -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.
Tsutsui
I
I
National Institute for Physiological Sciences, Myodaiji, Okazaki, 444-8585 Japan. tsutsui@nips.ac.jp
Ohkawa
T
T
D001693:Biological Transport, Active / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism; D002463:Cell Membrane Permeability; D004553:Electric Conductivity; D056890:Eukaryota / Q000502:physiology*; D006593:Hexokinase; D006863:Hydrogen-Ion Concentration; D008564:Membrane Potentials; D011188:Potassium / Q000378:metabolism; D011510:Proteolipids; D017494:Proton Pumps / Q000502:physiology*; D025262:Vacuolar Proton-Translocating ATPases
D011510:Proteolipids; D017494:Proton Pumps; C082471:ductin; D006593:Hexokinase; D025262:Vacuolar Proton-Translocating ATPases; D011188:Potassium