Journal Article

Evidence for Nucleotide-Dependent Passive H<sup>+</sup> Transport Protein in the Plasma Membrane of Barley Roots

Kousei Yamashita, Tetsuro Mimura and Ken-ichiro Shimazaki

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 44, issue 1, pages 55-61
Published in print January 2003 | ISSN: 0032-0781
Published online January 2003 | e-ISSN: 1471-9053 | DOI: https://dx.doi.org/10.1093/pcp/pcg005
Evidence for Nucleotide-Dependent Passive H+ Transport Protein in the Plasma Membrane of Barley Roots

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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-γ-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.

Keywords: Keywords: Barley — H+ channel — H+ transport — Plasma membrane H+-ATPase — Proteoliposome — Root.; Abbreviation: BTP, bis-tris-propane.

Journal Article.  4270 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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