Effects of perchlorate on depolarization-induced conformational changes in the junctional foot protein and Ca2+ release from sarcoplasmic reticulum.
Effects of perchlorate on depolarization-induced conformational changes in the junctional foot protein and Ca2+ release from sarcoplasmic reticulum.
复制标题
高氯酸盐对去极化诱导的足连接蛋白构象变化和肌浆网 Ca2 释放的影响。
DOI：
10.1021/bi00039a013
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发表时间：
1995
期刊：
影响因子：
2.9
通讯作者：
Ikemoto,N
中科院分区：
文献类型：
--
作者：
Yano,M;el-Hayek,R;Ikemoto,N
修订稿于 1995 年 8 月 7 日收到®摘要：高氯酸盐是文献报道的骨骼肌兴奋-收缩 (E-C) 耦合最有效的激活剂之一，但其作用的详细机制仍有待阐明。为了进一步解决高氯酸盐的作用模式，使用孤立的三联体模型研究了增加高氯酸盐浓度对电压依赖性（T 管介导）和电压非依赖性 Ca2+ 释放部分的影响。仅当 T 管部分被化学去极化时，低浓度的高氯酸盐 (< 10 mM) 才会激活 SR Ca2+ 释放。另一方面，较高浓度的高氯酸盐（30-100 mM）会显着激活 SR Ca2+ 释放，无论 T 管是否去极化。为了获得进一步的见解，我们监测了足连接蛋白 (JFP) 的构象变化，这可能是 EC 偶联的重要中间步骤 [Yano, M., El-Hayek, R., & Ikemoto, N.(1995) J. Biol.化学。 270, 3017—3021]，使用荧光标记的三联体制剂。同样，低浓度的高氯酸盐（< 10 mM）优先激活电压依赖性蛋白质构象变化，而较高浓度的高氯酸盐则显着激活电压无关的蛋白质构象变化。高氯酸盐与兰尼碱的结合增加仅发生在较高浓度范围内，其中电压无关的蛋白质构象变化被激活。这些结果表明，高氯酸盐通过作用于至少两个不同的步骤来激活 E-C 耦合：在较低浓度下，在 T 管到 JFP 信号传输步骤；在较低浓度下，在 T 管到 JFP 信号传输步骤上。在骨骼肌E—C耦合1功能的几种增强剂中，一组离液阴离子如高氯酸根(CIO4-)和硫氰酸根(SCN~)具有最显着的效果(Foulks et al., 1973; Foulks & Perry, 1979; Caputo, 1983; Gomolla et al., 1983; Liittgau 等，1983；Delay 等，1990；Dulhunty 等，1992）。对于这些活化阴离子，特别是高氯酸根的作用方式进行了广泛的研究。几毫摩尔高氯酸盐将电荷运动激活和 SR Ca2+ 释放的中点电位移动到
Revised Manuscript Received August 7, 1995® abstract: Perchlorate is one of the mostpotent activators of skeletal muscle excitation—contraction (E—C) coupling reported in the literature, but the detailed mechanism of its action remains to be elucidated. In an attempt to further resolve the mode of perchlorate action, the effects of increasing concentrations of perchlorate on the voltage-dependent (T-tubule-mediated) and voltage-independent portions of Ca2+ release were investigated using the isolated triad model. Low concentrations of perchlorate (< 10 mM) activated SR Ca2+ release only when the T-tubulemoiety was chemically depolarized. Higher concentrations of perchlorate (30—100 mM), on the other hand, produced significant activation of SR Ca2+ release, regardless of whether or not the T-tubule was depolarized. In order to gain further insights, we monitored the conformational change in the junctional foot protein (JFP), which presumably is an important intermediate step in EC coupling [Yano, M., El-Hayek, R., & Ikemoto, N.(1995) J. Biol. Chem. 270, 3017—3021], using the fluorescently labeled triad preparation. Again, low concentrations of perchlorate (< 10 mM) produced a preferential activation of voltage-dependent protein conformational change, while higher concentrations of perchlorate produced significant activation of voltage-independent protein conformational change. An increase in the ryanodinebinding by perchlorate occurred only in the higher concentration range where the voltage-independent proteinconformational change was activated. These results suggest that perchlorate activates E—C coupling by acting on at least two different steps: at lower concentrations, on the T-tubule-to-JFP signal transmission step; at higher concentrations, on the JFP directly.Among several potentiators of skeletal muscle E—C coupling1 function, a group of chaotropic anions such as perchlorate (CIO4-) and thiocyanate (SCN~) have the most remarkable effects (Foulks et al., 1973; Foulks & Perry, 1979; Caputo, 1983; Gomolla et al., 1983; Liittgau et al., 1983; Foulks & Morishita, 1985; Delay et al., 1990; Dulhunty et al., 1992). There are extensive studies on the mode of actions of these activating anions, especially of perchlorate. Several millimolar perchlorate shifts the midpoint potential for activation of charge movement and SR Ca2+ release to