Molecular dynamics in mouse atrial tumor sarcoplasmic reticulum.
Molecular dynamics in mouse atrial tumor sarcoplasmic reticulum.
复制标题
小鼠心房肿瘤肌浆网的分子动力学。
DOI：
10.1016/s0006-3495(95)80355-3
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发表时间：
1995
期刊：
影响因子：
--
通讯作者：
Thomas,DD
中科院分区：
文献类型：
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作者：
Voss,JC;Mahaney,JE;Jones,LR;Thomas,DD
我们直接确定了抑制肽受磷蛋白 (PLB) 对心脏肌浆网 (SR) 钙泵 (Ca-ATPase) 旋转动力学的影响。这是通过比较小鼠心室 SR 和小鼠心房 SR 来实现的，小鼠心室 SR 的 PLB 水平与其他哺乳动物相似，而小鼠心房 SR 实际上不含 PLB，因此具有更高的（不受调节的）钙泵活性。为了获得足够量的心房 SR，我们从心房肿瘤细胞中分离出膜。我们使用选择性且刚性地附着在 Ca-ATP 酶上的异硫氰酸赤藓红标记的时间分辨磷光各向异性来检测两种制剂中 Ca-ATP 酶的微秒旋转运动。由于存在不同的低聚物种类，两种制剂在 25°C 下的时间分辨磷光各向异性衰减都是多指数的。两种制剂中不同寡聚物的旋转相关时间相似，但心房肿瘤 SR 的总衰减幅度明显更大，表明较小部分的 Ca-ATP 酶分子以大聚集体形式存在。心室 SR 中 PLB 的磷酸化使大规模 Ca-ATPase 聚集体数量减少至与心房肿瘤 SR 相似的水平。通过硬脂酸自旋标记的电子顺磁共振检测到的脂质链迁移率（流动性）在两种制剂中非常相似，表明心房肿瘤 SR 中较高的蛋白质迁移率并不是由于较高的脂质流动性所致。我们得出的结论是，PLB 通过诱导 Ca-ATP 酶横向聚集来抑制，这可以通过磷酸化或去除 PLB 来缓解。
We have determined directly the effects of the inhibitory peptide phospholamban (PLB) on the rotational dynamics of the calcium pump (Ca-ATPase) of cardiac sarcoplasmic reticulum (SR). This was accomplished by comparing mouse ventricular SR, which has PLB levels similar to those found in other mammals, with mouse atrial SR, which is effectively devoid of PLB and thus has much higher (unregulated) calcium pump activity. To obtain sufficient quantities of atrial SR, we isolated the membranes from atrial tumor cells. We used time-resolved phosphorescence anisotropy of an erythrosin isothiocyanate label attached selectively and rigidly to the Ca-ATPase, to detect the microsecond rotational motion of the Ca-ATPase in the two preparations. The time-resolved phosphorescence anisotropy decays of both preparations at 25 degrees C were multi-exponential, because of the presence of different oligomeric species. The rotational correlation times for the different oligomers were similar for the two preparations, but the total decay amplitude was substantially greater for atrial tumor SR, indicating that a smaller fraction of the Ca-ATPase molecules exists as large aggregates. Phosphorylation of PLB in ventricular SR decreased the population of large-scale Ca-ATPase aggregates to a level similar to that of atrial tumor SR. Lipid chain mobility (fluidity), detected by electron paramagnetic resonance of stearic acid spin labels, was very similar in the two preparations, indicating that the higher protein mobility in atrial tumor SR is not due to higher lipid fluidity. We conclude that PLB inhibits by inducing Ca-ATPase lateral aggregation, which can be relieved either by phosphorylating or removing PLB.