Changes in the sarcoplasmic reticulum membrane profile induced by enzyme phosphorylation to E1 approximately P at 16 A resolution via time-resolved x-ray diffraction.
Changes in the sarcoplasmic reticulum membrane profile induced by enzyme phosphorylation to E1 approximately P at 16 A resolution via time-resolved x-ray diffraction.
复制标题
通过时间分辨 X 射线衍射，在 16 A 分辨率下，由酶磷酸化至 E1 大约 P 诱导肌质网膜轮廓的变化。
DOI：
10.1016/s0006-3495(88)83003-0
复制
发表时间：
1988
影响因子：
3.4
通讯作者：
Blasie,JK
中科院分区：
文献类型：
--
作者：
Pascolini,D;Herbette,LG;Skita,V;Asturias,F;Scarpa,A;Blasie,JK
分离的肌浆网(SR)膜的时间分辨X射线衍射研究提供了不同的电子密度分布，在没有可检测到的酶周转的情况下，与ATP引发的酶的磷酸化之前相比，在SR膜上的Ca~(2+)ATPase被暂时捕获在第一个磷酸化的中间状态，E_1约为P。这些衍射研究利用笼状三磷酸腺苷的闪光光解，在0-2℃的温度下进行，时间分辨率为2-5 S。在7-8℃，时间分辨率为0.2-0.5时，S对SR膜进行了类似的时间分辨X射线衍射研究，提供了在酶翻转条件下与酶磷酸化前相比，SR膜的Ca~(2+)-ATPase主要处于第一磷酸化中间态的不同电子密度分布。在相同的低分辨率(约40A)下比较，这两个不同的轮廓在性质上相似，但包含一些明显不同的特征，因此已通过阶跃函数模型分析进行了分析。这一分析是基于在7.5℃和-2℃酶磷酸化前SR膜的较高分辨率(16-17A)的x射线衍射研究中独立获得的两种不同电子密度分布的改进的阶跃函数模型。阶跃函数模型分析表明，两次时间分辨x射线衍射实验得到的低分辨率差异分布是由于Ca~(2+)-ATPase蛋白质量从SR膜脂双层的外单分子层到内单分子层的净运动。
Time-resolved x-ray diffraction studies of the isolated sarcoplasmic reticulum (SR) membrane have provided the difference electron density profile for the SR membrane for which the Ca2+ ATPase is transiently trapped exclusively in the first phosphorylated intermediate state, E1 approximately P, in absence of detectable enzyme turnover vs. that before ATP-initiated phosphorylation of the enzyme. These diffraction studies, which utilized the flash-photolysis of caged ATP, were performed at temperatures between 0 and -2 degrees C and with a time-resolution of 2–5 s. Analogous time-resolved x-ray diffraction studies of the SR membrane at 7–8 degrees C with a time resolution of 0.2–0.5 s have previously provided the difference electron density profile for the SR membrane for which the Ca2+ ATPase is only predominately in the first phosphorylated intermediate state under conditions of enzyme turnover vs. that before enzyme phosphorylation. The two difference profiles, compared at the same low resolution (approximately 40 A), are qualitatively similar but nevertheless contain some distinctly different features and have therefore been analyzed via a step-function model analysis. This analysis was based on the refined step-function models for the two different electron density profiles obtained independently from x-ray diffraction studies at higher resolution (16–17 A) of the SR membrane before enzyme phosphorylation at 7.5 and -2 degrees C. The step-function model analysis indicated that the low resolution difference profiles derived from both time-resolved x-ray diffraction experiments arise from a net movement of Ca2+ ATPase protein mass from the outer monolayer to the inner monolayer of the SR membrane lipid bilayer.(ABSTRACT TRUNCATED AT 250 WORDS)