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Biochemical pH clamp: the forgotten resource in membrane bioenergetics

Citation

Wegner, LH and Shabala, S, Biochemical pH clamp: the forgotten resource in membrane bioenergetics, New Phytologist, 225, (1) pp. 37-47. ISSN 0028-646X (2020) [Refereed Article]


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DOI: doi:10.1111/nph.16094

Abstract

Solute uptake and release by plant cells are frequently energized by coupling to H+ influx supported by the proton motive force (pmf). The pmf results from a stable pH difference between the apoplast and the cytosol, with bulk values ranging from 4.9 to 5.8 and from 7.1 to 7.5, respectively, in combination with a negative electrical membrane potential. The P‐type H+ ATPases pumping H+ from the cytosol into the apoplast at the expense of ATP hydrolysis are generally viewed as the only pmf source, exclusively linking membrane transport to energy metabolism. However, recent evidence suggests that pump activity may be insufficient to energize transport, particularly under stress conditions. Indeed, cytosolic H+ scavenging and apoplastic H+ generation by metabolism (denoted as ‘active’ buffering in contrast to the readily exhausted ‘passive’ matrix buffering) also stabilize the pH gradient. In the cytosol, H+ scavenging is mainly associated with malate decarboxylation catalyzed by malic enzyme, and via the GABA shunt of the tricarboxylic acid (TCA) cycle involving glutamate decarboxylation. In the apoplast, formation of bicarbonate from CO2, the end‐product of respiration, generates H+ at pH ≥ 6. Membrane potential is stabilized by K+ release and/or by anion uptake via ion channels. Finally, thermodynamic aspects of active buffering are discussed.

Item Details

Item Type:Refereed Article
Keywords:pH clamp, membrane potential, H+ ATPase
Research Division:Biological Sciences
Research Group:Plant Biology
Research Field:Plant Physiology
Objective Division:Plant Production and Plant Primary Products
Objective Group:Environmentally Sustainable Plant Production
Objective Field:Environmentally Sustainable Plant Production not elsewhere classified
UTAS Author:Shabala, S (Professor Sergey Shabala)
ID Code:136636
Year Published:2020 (online first 2019)
Web of Science® Times Cited:2
Deposited By:Agriculture and Food Systems
Deposited On:2020-01-11
Last Modified:2020-01-15
Downloads:0

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