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Electrogenicity of the Na + ‐ATPase from the marine microalga Tetraselmis (Platymonas) viridis and associated H + countertransport
Author(s) -
Balnokin Yurii V.,
Popova Larissa G.,
Andreev Igor M.
Publication year - 1999
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(99)01567-7
Subject(s) - vesicle , chemistry , atpase , ion transporter , ionophore , efflux , sodium , membrane potential , biophysics , nigericin , diaphragm pump , membrane , biochemistry , enzyme , biology , organic chemistry , materials science , micropump , nanotechnology
Sodium accumulation by the Na + ‐ATPase in the plasma membrane (PM) vesicles isolated from the marine alga Tetraselmis (Platymonas) viridis was shown to be accompanied by Δ Ψ generation across the vesicle membrane (positive inside) and H + efflux from the vesicle lumen. Na + accumulation was assayed with 22 Na + ; Δ Ψ generation was detected by recording absorption changes of oxonol VI; H + efflux was monitored as an increase in fluorescence intensity of the pH indicator pyranine loaded into the vesicles. Both ATP‐dependent Na + uptake and H + ejection were increased by the H + ionophore carbonyl cyanide m ‐chlorophenylhydrazone (ClCCP) while Δ Ψ was collapsed. The lipophilic anion tetraphenylboron ion (TPB − ) inhibited H + ejection from the vesicles and abolished Δ Ψ . Based on the effects of ClCCP and TPB − on H + ejection and Δ Ψ generation, the conclusion was drawn that H + countertransport observed during Na + ‐ATPase operation is a secondary event energized by the electric potential which is generated in the course of Na + translocation across the vesicle membrane. Increasing Na + concentrations stimulated H + efflux and caused the decrease in the Δ Ψ observed, thus indicating that Na + is likely a factor controlling H + permeability of the vesicle membrane.