Evidence for nucleotide-dependent passive H+ transport protein in the plasma membrane of barley roots.
Plasma membranes were isolated from barley roots by two-phase partitioning, and octylglucoside-soluble and -insoluble fractions were obtained. The insoluble fractions were reconstituted into liposomes, and the plasma membrane H(+)-ATPase was shown to participate in MgATP-dependent H(+) transport activity. The H(+) transport was decreased when the octylglucoside-soluble fraction was reconstituted together with the insoluble fraction. The decrease was not due to inhibition of the H(+)-ATPase, but rather was likely due to the increased H(+) leakage from the proteoliposome. The octylglucoside-soluble fraction was, therefore, reconstituted in the liposomes and the passive H(+) transport was determined using the pH jump method. A pH gradient across the membranes was generated by the pH jump, and the gradient was found to be dissipated by passive H(+) transport. The H(+) transport required ATP, K(+), and valinomycin. The H(+)-transport also occurred when ADP, AMP, GTP, or ATP-gamma-S was present instead of ATP, and did not occur when the octylglucoside-soluble fraction was boiled before the reconstitution. These findings suggest that nucleotide-dependent H(+ )transport protein is present in the plasma membrane of root cells.
Yamashita
Kousei
K
Department of Biology, Faculty of Science, Kyushu University, Ropponmatsu 4-2-1, Fukuoka, 810-8560 Japan.
Mimura
Tetsuro
T
Shimazaki
Ken-ichiro
K
D000255:Adenosine Triphosphate / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D005960:Glucosides / Q000494:pharmacology; D001467:Hordeum / Q000502:physiology*; D009711:Nucleotides / Q000494:pharmacology*; D018517:Plant Roots / Q000502:physiology*; D011188:Potassium / Q000494:pharmacology; D006180:Proton-Translocating ATPases / Q000187:drug effects / Q000378:metabolism*; D014634:Valinomycin / Q000494:pharmacology
D005960:Glucosides; D009711:Nucleotides; D014634:Valinomycin; C018619:octyl-beta-D-glucoside; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases; D011188:Potassium