Chiang W, Greaser M L
Muscle Biology Laboratory, University of Wisconsin-Madison, 53706, USA.
J Muscle Res Cell Motil. 2000 May;21(4):321-33. doi: 10.1023/a:1005650706464.
Two filamin isoforms were purified from bovine tissues and characterized. Muscle filamin and nonmuscle filamin had different SDS gel mobilities, proteolytic digestion patterns, myofibrillar binding distributions and myofibril binding affinities. The muscle specific filamin had an apparent molecular weight of 265 kDa and bound primarily to the Z-lines of myofibrils but also to the I-bands near the Z-lines. The nonmuscle specific filamin had an apparent molecular weight of 275 kDa and bound exclusively to the Z-lines of myofibrils. The filamin myofibril binding was studied quantitatively. Plotting bound fraction (mg filamin/mg myofibril) vs. equilibrium concentration of free filamin yielded a biphasic binding curve. The first hyperbolic binding phase described the binding of filamin to myofibrils but the second phase appeared to be nonspecific due to filamin aggregation. The muscle filamin had a significantly lower (P < 0.05) apparent binding affinity to myofibrils than nonmuscle filamin. However, the muscle filamin showed a significantly higher (P < 0.05) saturation value for myofibrils than nonmuscle filamin. The binding of phosphorylated filamin to myofibrils was significantly lower (P < 0.05) than the corresponding native proteins for both filamin isoforms.
从牛组织中纯化并鉴定了两种细丝蛋白亚型。肌肉细丝蛋白和非肌肉细丝蛋白具有不同的SDS凝胶迁移率、蛋白水解消化模式、肌原纤维结合分布和肌原纤维结合亲和力。肌肉特异性细丝蛋白的表观分子量为265 kDa，主要与肌原纤维的Z线结合，但也与Z线附近的I带结合。非肌肉特异性细丝蛋白的表观分子量为275 kDa，仅与肌原纤维的Z线结合。对细丝蛋白与肌原纤维的结合进行了定量研究。绘制结合分数（毫克细丝蛋白/毫克肌原纤维）与游离细丝蛋白平衡浓度的关系图，得到一条双相结合曲线。第一个双曲线结合阶段描述了细丝蛋白与肌原纤维的结合，但由于细丝蛋白聚集，第二个阶段似乎是非特异性的。肌肉细丝蛋白对肌原纤维的表观结合亲和力明显低于非肌肉细丝蛋白（P < 0.05）。然而，肌肉细丝蛋白对肌原纤维的饱和值明显高于非肌肉细丝蛋白（P < 0.05）。两种细丝蛋白亚型的磷酸化细丝蛋白与肌原纤维的结合均明显低于相应的天然蛋白（P < 0.05）。
