Sussman M A, Ito M, Daniels M P, Flucher B, Buranen S, Kedes L
Department of Biochemistry and Molecular Biology, University of Southern California School of Medicine, Hoffman Medical Research, Los Angeles, CA 90033, USA.
Cell Tissue Res. 1996 Aug;285(2):287-96. doi: 10.1007/s004410050646.
Tropomodulin is a 40.6-kDa isoform-specific tropomyosin-binding protein which inhibits actin filament elongation from the slow-growing (pointed) end and localizes at or near the pointed ends of thin filaments in rat skeletal muscle. Immunofluorescent localization using affinity-purified anti-tropomodulin antibodies in avian myofibril preparations demonstrates novel immunoreactivity at the Z-disc in addition to the previously reported localization at the periphery of I-Z-I brushes where actin filaments terminate. Identical results were obtained using antibody preparations generated against either bacterially expressed tropomodulin or human erythrocyte tropomodulin. Chicken muscle preparations contain Mr 43000 polypeptides which bind antibodies generated against tropomodulin in Western blot analysis, as well as 125I-labeled tropomyosin in blot overlays. Tropomodulin mRNA expression in adult muscle was confirmed by RNase protection assays, and the sequence of our tropomodulin cDNA amplified from chicken muscle mRNA preparations by polymerase chain reaction closely matches clones selected by chicken muscle cDNA library screening. The novel immunolocalization we report raises new possibilities for the role of tropomodulin in the organization of avian skeletal muscle at the Z-disc. We conclude that tropomodulin is likely to be important in striated muscle biology as a structural component in the Z-disc region which participates in the process of thin filament organization and assembly.
原肌球蛋白调节蛋白是一种40.6 kDa的亚型特异性原肌球蛋白结合蛋白，它抑制肌动蛋白丝从缓慢生长的（钝端）末端延长，并定位于大鼠骨骼肌细肌丝钝端或其附近。在禽肌原纤维制剂中使用亲和纯化的抗原肌球蛋白调节蛋白抗体进行免疫荧光定位，结果显示除了先前报道的在肌动蛋白丝终止的I-Z-I刷外周的定位外，在Z盘处还有新的免疫反应性。使用针对细菌表达的原肌球蛋白调节蛋白或人红细胞原肌球蛋白产生的抗体制剂也得到了相同的结果。在蛋白质印迹分析中，鸡肌肉制剂含有能与抗原肌球蛋白调节蛋白抗体结合的43000 Mr多肽，以及在印迹覆盖实验中能与125I标记的原肌球蛋白结合的多肽。通过核糖核酸酶保护试验证实了原肌球蛋白调节蛋白mRNA在成年肌肉中的表达，并且我们通过聚合酶链反应从鸡肌肉mRNA制剂中扩增的原肌球蛋白调节蛋白cDNA序列与通过鸡肌肉cDNA文库筛选选择的克隆紧密匹配。我们报道的新的免疫定位为原肌球蛋白调节蛋白在禽骨骼肌Z盘组织中的作用提出了新的可能性。我们得出结论，原肌球蛋白调节蛋白作为Z盘区域的结构成分，参与细肌丝的组织和组装过程，在横纹肌生物学中可能很重要。
