Functional evidence of a transmembrane channel within the Ca2+ transport ATPase of sarcoplasmic reticulum

FEBS Letters

de Meis, Leopoldo¹  Inesi, Giuseppe¹ 

[1] Departamento de Bioquimica, Instituto de Ciencias Medicas, Universidade Federal Rio de Janeiro, Rio de Janeiro, RJ 21910, Brazil

关键词: Ca2+ efflux;    ATPase channel;    Sarcoplasmic reticulum;    Thapsigargin;    Phenothiazine;   

DOI  :  10.1016/0014-5793(92)80093-V

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Ca²⁺ efflux can be studied conveniently following dilution of sarcoplasmic reticulum (SR) vesicles preloaded with ⁴⁵Ca²⁺ by active transport. The rates of efflux are highly dependent on ATPase substrates and cofactors (P_i, Mg²⁺, Ca²⁺ and ADP) in the efflux medium. On the other hand, pbenothiazines stimulate efflux through a passive permeability channel with no coupled catalytic events. Efflux activation by manipulation of catalytically active ATPase ligands, as well as by the catalytically inactive phenothiazines, can be prevented by thapsigargin, which is a highly specific inhibitor of the Ca²⁺-ATPase. This demonstrates that the passive channel activated by phenothiazines is an integral part of the ATPase, and can operate either uncoupled or coupled to catalytic events.

【 授权许可】

Unknown