Characterization of enzymatic property plant specific class VIII myosin

肌球蛋白是将化学能转化为机械运动的运动蛋白。系统发育分析表明，肌球蛋白至少由35类组成。在这些纲中，植物只有两个纲，即第VIII纲和第Xi纲。尽管拟南芥VIII类肌球蛋白ATM.我们发现肌动蛋白在ATm上的滑动速度很慢，ATm上肌动蛋白激活的ATP酶活性很低。此外，我们还发现游离Mg^<2+>对肌动蛋白的滑动速度和肌动蛋白激活的ATP酶活性均有调节作用。用停流装置进行的动力学分析表明，游离Mg^2+控制ADP从肌动蛋白-肌球蛋白-ADP中解离的速率。

Myosin is motor protein which converts chemical energy into mechanical movement. Phylogenetic analysis revealed that myosins consist of at least 35 classes. Among these classes, plant has only 2 classes, namely, class VIII and class XI. although enzymatic and motile properties of Arabidopsis class VIII myosin, ATM. We have found that actin sliding velocity by ATm was very slow and actin-activated ATPase activity of ATm was very low. In addition, we also found that both the actin sliding velocity and the actin-activated ATPase activities were regulated by free Mg^<2+>. Kinetic analyses using stopped flow apparatus revealed that free Mg^<2+>controled ADP dissociation rate from acto-myosin-ADP.