Evidence for direct involvement of the sarcoplasmic reticulum Ca2+‐ATPase in a passive monovalent cation (K+/Na+) exchange

[摘要]

A specific inhibitor of SERCA-pumps, thapsigargin (TG) was used to demonstrate the direct involvement of the SR Ca²⁺-ATPase in passive K⁺/Na⁺ exchange. The K⁺-potential variations across vesicle membranes were measured in the absence of ATP with a fluorescent probe: 3,3′-dipropylthiodicarbocyanine iodide. Addition of EGTA dissipates the K⁺-potential whereas the presence of TG abolishes this effect. Our data prove that the Ca²⁺-ATPase translocates monovalent cations at a rate similar to the E₂→E₁ conformational change.

[学科分类] 生物化学/生物物理

[关键词] Ca2+-ATPase;Sarcoplasmic reticulum;K+/Na+ exchange;Thapsigargin;Potential sensitive dye;DiSC3(5);EGTA;ethylene glycol-bis(β-aminoethyl ether)-N;N;N′;N′-tetraacetic acid;ATP;adenosine-5′-triphosphate;SR;sarcoplasmic reticulum;DMSO;dimethyl sulfoxide;DiSC3(5);3;3′dipropylthiodicarbocyanine iodide;MOPS;3-(N-morpholino)propane-sulfonic acid