Regulatory mechanism in gene expression of regulatory proteins in cardiac and vascular smooth muscles

Calponin是我们在平滑肌细胞中发现的肌动蛋白、原肌球蛋白结合蛋白。本课题研究了钙蛋白在血管内皮细胞中的定位及其生理功能。(1)获得了含有肌动蛋白、原肌球蛋白、钙蛋白和钙蛋白的细丝，其摩尔比为7：0.9：0.6：0.7。肌动蛋白和降钙素蛋白沿大鼠主动脉平滑肌细胞应力纤维共定位。(2)体外研究了降钙素蛋白的功能。钙蛋白抑制肌球蛋白镁ATPase活性，呈剂量依赖关系。这种抑制作用不依赖于钙离子。肌球蛋白酶活性的降低与肌钙蛋白与肌动蛋白-促胰蛋白酶细丝的结合有关。Caldesmon进一步抑制了钙蛋白对硫代磷酸化肌球蛋白镁ATPase活性的抑制作用。钙调素可逆转钙调素对肌球蛋白镁ATPase的抑制作用。本研究结果提示，降钙素可能是肌纤维细丝的抑制成分。(3)从鸡肌肌和大鼠主动脉中克隆了SM22基因。从鸡肌肌组织中克隆的SM2 2基因全长1214bp，含有一个开放阅读框，编码2 0 0个氨基酸，相对分子质量为22214。预测的氨基酸序列与Pearlstone等人测定的序列完全一致。他发现了这种蛋白质，除了C末端的两个额外残基，异亮氨酸和丝氨酸。从大鼠主动脉中提取的基因全长为1186bp。全长，编码201个氨基酸(Mr 22602)。预测的氨基酸序列与鸡肌胃SM22有85%的同源性。

Calponin is actin-, tropomyosin binding protein which we found in the smooth muscle cells. In this project we studied the localization of calponin in smooth muscle cell and the physiological function of calponin.(1) We obtained thin filaments which contained actin, tropomyosin, caldesmon and calponin in molar rations of 7 : 0.9 : 0.6 : 0.7. Co-localization of actin and calponin was shown along stress fibers of smooth muscle cells from rat aorta.(2) We studied the function of calponin in vitro. Calponin inhibited the actinactivated myosin MgATPase activity in a dose-dependent manner. This inhibition was Ca-independent. The decrease in enzymatic activity of myosin was correlated with binding of calponin to actin-tropgmypsin filaments. Caldesmon showed a further inhibition of the calponin-induced inhibition of MgATPase activity of the thiophosphorylated myosin. Calponin-induced inhibition of the myosin MgATPase was reversed by the addition of calmodulin in the presence of Ca. These results suggest that calponin acts as an inhibitory component of smooth muscle thin filaments.(3) We performed cDNA cloning of SM22 from the chicken gizzard smooth muscle and rat aorta smooth muscle. Cloned cDNA encoding SM22 from the chicken gizzard smooth muscle had a total length of 1214bp and contained a single open reading frame which encodes 200 amino acids with a calculated molecular weight 22214. The predicted amino acid sequence was in complete agreement with the sequence determined by Pearlstone et al. who discovered the protein, except for two additional residues, isoleucine and serine at the C-terminus. The cDNA from rat aorta was 1186bp. in length and encoded 201 amino acids (Mr 22602). The predicted amino acid sequence showed an 85% Tdentity with the chicken gizzard SM22.