天然アクトミオシンにアクチンを加えたときのカルシウム感受性

概要

論文の詳細を見る
The calcium sensitivity of myosin B (natural aclomyosin) was investigated at low ionic strength in the presence of added myosin or F-action of Straub type. The Mg-activated ATPase activity at a very low ionic strength was greatly enhanced by the addition of myosin or F-actin. The weight ratio to myosin B was 1:1 or larger. However, when an excess amount of myosin was added to myosin B, the calcium sensitivity was not altered: the ATPase activity was remarkably decreased by the removal of free calcium ions. On the other hand, the addition of F-actin (1:1 ratio by weight) resulted in loss of the calcium sensitivity. The ATPase activity was not appreciably affected by EGTA, and also the onset of superprecipitation was observed. In this case, addition of Ebashi's native tropomyosin (weight ratio of 1:4 to F-actin added) completely recovered the calcium sensitivity: the APTase activity was inhibited by EGTA and clearing response occurred instead of superprecipitation. These observations are in good agreement with our previous view that native tropomyosin exerts its action through the binding to F-actin.
1967-08-15