Fuchs F, Fox C
Biochim Biophys Acta. 1982 Jan 20;679(1):110-5. doi: 10.1016/0005-2728(82)90261-4.
A simple double-isotope procedure has been developed for making simultaneous measurements of bound Ca2+ and relative force in glycerinated rabbit psoas bundles containing two fibers. With this preparation it is possible to study Ca2+-troponin interactions coincident with MgATP-induced force development. Over the free [Ca2+] range 6 . 10(-8)--1.2 . 10(-5) M the bound Ca2+ varied from 0.25 to 1.65 mumol/g protein. The free [Ca2+] at half-maximal Ca2+ saturation was 2 . 10(-7) M while that a half-maximal force was 5 . 10(-7) M. Half-maximal Ca2+ saturation was associated with 20% maximal force. The force-[Ca2+] saturation curve showed a steep rise in slope at greater than half saturation. The observed relationship was consistent with a model in which multiple occupancy of troponin Ca2+-binding sites is essential for initiation of cross-bridge cycling.
已开发出一种简单的双同位素程序，用于同时测量含有两根纤维的甘油化兔腰大肌束中的结合钙（Ca2+）和相对力。利用这种制备方法，可以研究与MgATP诱导的力发展同时发生的Ca2+ -肌钙蛋白相互作用。在游离[Ca2+]范围6×10(-8) - 1.2×10(-5) M内，结合钙从0.25变化到1.65 μmol/g蛋白质。Ca2+饱和度达到一半时的游离[Ca2+]为2×10(-7) M，而力达到一半时的游离[Ca2+]为5×10(-7) M。Ca2+饱和度达到一半时对应20%的最大力。力-[Ca2+]饱和度曲线在饱和度大于一半时斜率急剧上升。观察到的关系与一种模型一致，在该模型中，肌钙蛋白Ca2+结合位点的多重占据对于启动横桥循环至关重要。
