Svensson C, Morano I, Arner A
Department of Physiology and Neuroscience, Lund University, Sweden.
J Cell Biochem. 1997 Nov 1;67(2):241-7. doi: 10.1002/(sici)1097-4644(19971101)67:2<241::aid-jcb9>3.0.co;2-x.
The role of myosin isoforms in determining contractile filament velocity in the atrium and ventricle of the pig heart was studied by measuring the motion of fluorescently labeled actin over myosin (in vitro motility assay). A rapid and relatively simple method for purification of myosin from small tissue samples was used. The relative extent of light chain-2 phosphorylation was about 30% in both atrial and ventricular myosin extracts. Although the extracted myosin was not free from contaminating proteins, mainly actin, the mean velocity at optimal pH and 32 degrees C of both atrial (3.3 microns/s) and ventricular (2.3 microns/s) myosin were similar to those obtained using extensively purified myosin. The filament sliding velocities using isolated myosin and actin are lower than those estimated from previously published experiments on skinned fiber preparations, which might reflect an influence on sliding velocity by the filament organization or regulatory proteins in the muscle fiber. However, the ratio between velocities of atrial and ventricular myosin was similar in the motility assay (1.5) and muscle fiber experiments (1.6), which might suggest that these two methods reflect the same fundamental processes in cardiac contraction and that the difference in filament sliding velocity between the atrium and ventricle of the pig heart is determined my their myosin isoforms.
通过测量荧光标记的肌动蛋白在肌球蛋白上的运动（体外运动测定法），研究了肌球蛋白同工型在确定猪心脏心房和心室收缩丝速度中的作用。采用了一种从少量组织样本中纯化肌球蛋白的快速且相对简单的方法。心房和心室肌球蛋白提取物中轻链 -2 的磷酸化相对程度约为 30%。尽管提取的肌球蛋白并非完全不含污染蛋白，主要是肌动蛋白，但在最佳 pH 和 32℃条件下，心房肌球蛋白（3.3 微米/秒）和心室肌球蛋白（2.3 微米/秒）的平均速度与使用大量纯化肌球蛋白所获得的速度相似。使用分离的肌球蛋白和肌动蛋白时，丝滑动速度低于先前发表的关于去表皮纤维制剂实验所估计的速度，这可能反映了肌纤维中丝组织或调节蛋白对滑动速度的影响。然而，在运动测定法（1.5）和肌纤维实验（1.6）中，心房和心室肌球蛋白速度之间的比率相似，这可能表明这两种方法反映了心脏收缩中相同的基本过程，并且猪心脏心房和心室之间丝滑动速度的差异是由它们的肌球蛋白同工型决定的。
