CHARACTERIZATION OF VERTEBRATE MYOSIN I

鸡肠道刷状缘上皮细胞含有钙调蛋白 110 kDa的结合蛋白，已被证明是肌球蛋白I型 分子。可能有三种钙调蛋白分子与 每条重链。这种肌球蛋白不形成细丝，但确实有一个 肌动蛋白激活的镁ATPase活性等性质较多 传统的双头肌球蛋白分子。我们已经证明它是有能力的 在体外运动性试验中的肌动蛋白细丝的移位。机动性 在高钙条件下，肌动蛋白激活的镁ATP酶活性受到抑制 由于部分钙调蛋白解离而产生的浓度 分子。钙调素重现运动和肌动蛋白激活 镁ATPase的活性。原肌球蛋白也与肌动蛋白细丝结合 抑制运动性和肌动蛋白激活的镁ATPase活性 肌动蛋白-原肌球蛋白对肌球蛋白的亲和力降低。有趣的是， 免疫荧光数据显示肌球蛋白I不与 原肌球蛋白富集区组织培养细胞。

Chicken intestinal brush border epithelial cells contain a calmodulin binding protein of 110 kDa which has been shown to be a myosin I type molecule. There are probably three calmodulin molecules associated with each heavy chain. This myosin does not form filaments, but does have an actin-activated MgATPase activity and other properties of the more conventional two-headed myosin molecules. We have shown that it is capable of translocating actin filaments in an in vitro motility assay. Motility and actin-activation of the MgATPase activity is inhibited at high calcium concentrations due to a dissociation of a fraction of the calmodulin molecules. Readdition of calmodulin restores motility and actin-activation of the MgATPase activity. Tropomyosin binding to the actin filaments also inhibits motility and actin-activated MgATPase activity due to a large decrease in the affinity of actin-tropomyosin for myosin. Interestingly, immunofluorescent data demonstrates that myosin I does not co-localize to tropomyosin-rich regions of tissues culture cells.