Electrogenicity of the Na+‐ATPase from the marine microalga Tetraselmis (Platymonas) viridis and associated H+ countertransport

FEBS Letters

Popova, Larissa G.¹  Balnokin, Yurii V.¹  Andreev, Igor M.¹ 

[1] Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya 35, Moscow 127276, Russia

关键词: Marine alga;    Na+-ATPase;    Na+/H+ countertransport;    Na+ pump;    Plasma membrane;    Tetraselmis (Platymonas) viridis;    BTP;    1;    3-bis-(tris(hydroxymethyl)methylamino)propane;    ClCCP;    carbonyl cyanide m-chlorophenylhydrazone;    EGTA;    ethylene glycol-bis(β-aminoethyl ether)-N;    N;    N′;    N′-tetraacetic acid;    HEPES;    N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid;    MES;    2-[N-morpholino]ethanesulfonic acid;    oxonol VI;    bis-(3-propyl-5-oxoisoxazol-4-yl)pentamethine oxonol;    PM;    plasma membrane;    pyranine;    8-hydroxy-1;    3;    6-pyrene trisulfonate;    TPB−;    tetraphenylboron ion;    ΔΨ;    membrane electric potential difference;   

DOI  :  10.1016/S0014-5793(99)01567-7

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

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 ΔΨ generation across the vesicle membrane (positive inside) and H⁺ efflux from the vesicle lumen. Na⁺ accumulation was assayed with ²²Na⁺; ΔΨ 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 ΔΨ was collapsed. The lipophilic anion tetraphenylboron ion (TPB⁻) inhibited H⁺ ejection from the vesicles and abolished ΔΨ. Based on the effects of ClCCP and TPB⁻ on H⁺ ejection and ΔΨ 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 ΔΨ observed, thus indicating that Na⁺ is likely a factor controlling H⁺ permeability of the vesicle membrane.

【 授权许可】

Unknown