title: Zinc ions block H⁺/OH⁻ channels in Chara australis.
abstract: Chara australis cells exposed to media of pH 10 and above exhibit high conductance, arising from the opening of H⁺/OH⁻ channels in the plasma membrane. This high conductance can be totally inhibited by 1.0 mm ZnCl₂ and restored by 0.5 mm 2-mercaptoethanol (ME). Important for carbon fixation, H⁺/OH⁻ channels play a key role in cell pH banding. Banding was also shown to be abolished by 1.0 mm ZnCl₂ and restored in some cells by ME. The proton pump is also involved in banding, but was little affected by ZnCl₂ over the periods needed for the inhibition of H⁺/OH⁻ channels. Previously, we postulated that H⁺/OH⁻ channels open transiently at the onset of saline stress in salt-sensitive C. australis, causing membrane potential difference (PD) noise; and remain open in latter stages of saline stress, contributing to cell deterioration. ZnCl₂ totally inhibited the saline noise and the upwardly concave I/V characteristics associated with the putative H⁺/OH⁻ currents. Again, ME reversed both these effects. We discuss the mode of action of zinc ions and ME with reference to animal voltage-gated H⁺ channels and water channels.
authors.affiliation: School of Physics, Membrane Biophysics, The University of NSW, Sydney, New South Wales 2052, Australia.
authors.forename: Sabah
authors.initials: S
authors.lastname: Al Khazaaly
authors.forename: Mary J
authors.initials: MJ
authors.lastname: Beilby
mesh_terms: D044784:Chara / Q000378:metabolism*; D006878:Hydroxides / Q000378:metabolism*; D007473:Ion Channels / Q000037:antagonists & inhibitors*; D011522:Protons; D015032:Zinc / Q000378:metabolism*
chemical_list: D006878:Hydroxides; D007473:Ion Channels; D011522:Protons; D015032:Zinc