Characterization of the Ca2+- or Mg2+-ATPase of transverse tubule membranes isolated from rabbit skeletal muscle.

摘要: Transverse tubule membranes isolated from rabbit skeletal muscle have high levels of a Ca2+- or Mg2+-ATPase with Km values for Ca-ATP Mg-ATP in the 0.2 mM range, but do not display detectable ATPase activity activated by micromolar [Ca2+]. The transverse enzyme is less temperature pH dependent than Ca2+-ATPase sarcoplasmic reticulum and hydrolyzes equally well ATP, ITP, UTP, CTP, GTP. Of several ionic, non-ionic, zwitterionic detergents tested, only lysolecithin solubilizes membrane while preserving activity. After extraction about 50% proteins solubilization most remains bound, indicating that an intrinsic enzyme. A second remaining results partial purification Sedimentation Mg2+-ATPase, partially purified solubilization, through continuous sucrose gradient devoid detergent leads to additional purification, overall 3- 5-fold factor. preparation contains two main protein components molecular weights 107,000 30,000. Cholesterol, which highly enriched membrane, copurifies vesicles also ATP-dependent calcium transport affected phosphate oxalate. possibility responsible Ca2+ displayed tubules discussed.