Mornet D, Harricane M C, Audemard E
Centre de Biochimie Macromoléculaire du CNRS, INSERM U 249, Université Montpellier I, France.
Biochem Biophys Res Commun. 1988 Sep 15;155(2):808-15. doi: 10.1016/s0006-291x(88)80567-9.
Specific thrombin proteolysis of native 120-kDa gizzard caldesmon gave rise to a major cleavage into an N-terminal 90-kDa and a C-terminal 35-kDa fragment. Fluorescent labeling, cosedimentation, passage through an affinity column, and carbodiimide crosslinking with actin revealed that the 35-kDa purified segment of the molecule contains the actin and the calcium-calmodulin binding regions. Electron microscopic analysis of its actin complex demonstrated that the 35-kDa segment possesses the bundling properties of the intact molecule. Thus, a possible pathway for the expression of the caldesmon regulatory function during smooth muscle contraction would be a conformational change twisting the helicoïdal structure of the actin filament, which occurs when the 35-kDa caldesmon portion binds to it.
天然120 kDa肌胃钙调蛋白的特异性凝血酶蛋白水解作用产生了一个主要的裂解产物，即一个N端90 kDa片段和一个C端35 kDa片段。荧光标记、共沉降、通过亲和柱以及与肌动蛋白的碳二亚胺交联表明，该分子的35 kDa纯化片段包含肌动蛋白结合区域和钙调蛋白结合区域。对其肌动蛋白复合物的电子显微镜分析表明，35 kDa片段具有完整分子的成束特性。因此，平滑肌收缩过程中钙调蛋白调节功能表达的一个可能途径是，当35 kDa钙调蛋白部分与之结合时，肌动蛋白丝的螺旋结构发生扭曲的构象变化。
