The interaction of calcium and ryanodine with cardiac sarcoplasmic reticulum.
The interaction of calcium and ryanodine with cardiac sarcoplasmic reticulum.
复制标题
钙和兰尼定与心脏肌浆网的相互作用。
DOI：
10.1016/0005-2736(87)90336-1
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发表时间：
1987
期刊：
影响因子：
--
通讯作者：
Feher,JJ
中科院分区：
文献类型：
--
作者：
Alderson,BH;Feher,JJ
[~3H]兰尼定与心肌肌浆网小泡的结合依赖于钙离子浓度。在无钙的情况下，结合似乎是非特异性的，因为它在20μM ryanodine时不显示饱和。当兰尼定浓度在10~265μ之间变化时，钙的表观Km值在2~0.8 nM之间变化。[~3H]Ryanodine结合的钙依赖性希尔系数接近2。对Ryanodine结合的Scatchard分析表明，Ryanodine有一个高亲和力结合部位，其Bmax为5.2±0.4pmol/mg，AKd6.8±0.1 nM。在高亲和力部位饱和的条件下预孵育并未导致钙摄取率的刺激，表明钙通道关闭。钙摄取率只有在较高浓度的兰尼定(Km=17μM)时才有刺激作用。这种钙摄取率的刺激也需要亚微摩尔范围的钙。这些数据支持兰诺定与低亲和力位点(Km约17μM)结合是导致钙释放通道关闭和随后肌浆网钙摄取增加的假说。因为Ryanodine结合位点的数量比钙离子转运泵的数量少得多，所以该通道可能与钙转运泵不同。
The binding of [3H]ryanodine with cardiac sarcoplasmic reticulum vesicles depends on the calcium concentration. Binding in the absence of calcium appears to be non-specific because it shows no saturation up to 20 μM ryanodine. The apparentKmvalue for calcium varied between 2 and 0.8 μM when the ryanodine concentration varied between 10 and 265 nM. The Hill coefficient for the calcium dependence of [3H]ryanodine binding was near two. Scatchard analysis of ryanodine binding indicated a high-affinity site with aBmaxof 5.2 ± 0.4 pmol/mg with aKdof 6.8 ± 0.1 nM. Preincubation under conditions in which the high-affinity sites were saturated did not result in stimulation of the calcium uptake rate indicative of closure of the calcium channel. Stimulation of calcium uptake rate occurred only at higher concentrations of ryanodine (apparentKm= 17μM). This stimulation of the calcium uptake rate also required calcium in the submicromolar range. The data obtained support the hypothesis that ryanodine binding to the low-affinity site (Kmabout 17 μM) is responsible for closure of the calcium release channel and the subsequent increase in the calcium uptake rate of the sarcoplasmic reticulum. Because the number of ryanodine-binding sites is much less than the number of calcium transport pumps the channel is probably distinct from the pump.