Dulon D, Bréthes D, Chevallier J
Institut de Biochimie Cellulaire et de Neurochimie du CNRS, Bordeaux, France.
J Bioenerg Biomembr. 1987 Oct;19(5):505-14. doi: 10.1007/BF00770033.
The dependence of the Ca2+-ATPase activity of sarcoplasmic reticulum vesicles upon the intravesicular concentration of calcium accumulated after active uptake was studied. The internal calcium concentration was modified by addition of the ionophore A23187 at the steady state of accumulation. About half of the calcium accumulated could be released at low ionophore concentration without any concomitant activation of the Ca2+-ATPase. This population of calcium might consist of calcium free in the lumen of the vesicles or bound to the bilayer at sites which do not interact with the ATPase activity. At higher concentrations of ionophore (above 1.75 nmol A23187/mg protein) the release of calcium activated this enzyme. This phenomenon was independent of the extravesicular calcium concentration and might be explained by assuming second species of calcium ions bound to the inner side of the membrane and in close functional interaction with the Ca2+-ATPase.
研究了肌浆网囊泡的Ca2+-ATP酶活性对主动摄取后积累的囊泡内钙浓度的依赖性。在积累的稳态下，通过添加离子载体A23187来改变内部钙浓度。在低离子载体浓度下，约一半积累的钙可以释放，而不会伴随Ca2+-ATP酶的任何激活。这群钙可能由囊泡腔内游离的钙或结合在不与ATP酶活性相互作用的位点的双层膜上的钙组成。在较高浓度的离子载体（高于1.75 nmol A23187/mg蛋白质）下，钙的释放激活了这种酶。这种现象与囊泡外钙浓度无关，可能是由于假定第二种钙离子结合在膜内侧并与Ca2+-ATP酶有紧密的功能相互作用来解释。
