Bull R, Marengo J J
Departamento de Fisiología y Biofísica, Facultad de Medicina, Universidad de Chile, Santiago.
FEBS Lett. 1993 Oct 4;331(3):223-7. doi: 10.1016/0014-5793(93)80341-q.
Calcium channels derived from sarcoplasmic reticulum of frog skeletal muscle were fused with planar lipid bilayers. Fractional open times displayed two types of calcium dependence: (i) blockable channels showed a bell-shaped calcium dependence with an activation constant of 4.5 microM, a Hill coefficient for activation of 1.46 and a blocking constant of 226 microM, and (ii) non-blockable channels displayed a sigmoidal calcium dependence with an activation constant of 1.1 microM and a Hill coefficient of 1.42; no blocking effect was seen with calcium up to 0.5 mM. These two types of calcium dependence may underlie the coexistence of two different pathways for calcium release in frog skeletal muscle.
将源自青蛙骨骼肌肌浆网的钙通道与平面脂质双层融合。开放时间分数显示出两种类型的钙依赖性：（i）可阻断通道呈现钟形钙依赖性，激活常数为4.5微摩尔，激活的希尔系数为1.46，阻断常数为226微摩尔；（ii）不可阻断通道呈现S形钙依赖性，激活常数为1.1微摩尔，希尔系数为1.42；在钙浓度高达0.5毫摩尔时未观察到阻断作用。这两种类型的钙依赖性可能是青蛙骨骼肌中两种不同钙释放途径共存的基础。
