Heeley D H, Golosinska K, Smillie L B
J Biol Chem. 1987 Jul 25;262(21):9971-8.
Using a nonpolymerizable form of tropomyosin (NPTM) we have investigated the interactions between the T1 (residues 1-158) and T2 (residues 159-259) regions of troponin T and the other components of the thin filament at 50 mM KCl +/- Ca2+. Under these conditions the binding of NPTM to F-actin is fully restored by whole troponin (+/- Ca2+), and in each case, retains a residual degree of cooperativity as demonstrated by Scatchard and Hill plots. Fragment T2 alone had a small inductive effect on the interaction of NPTM with F-actin. In the presence of troponin I, this interaction is increased to a level which exceeds that observed with either component alone. The effects of T2 and troponin I are moderately (-Ca2+) and markedly (+Ca2+) reduced by troponin C. While fragment T1 alone did not promote induction, it accentuated the effects of T2 and troponin I. Since T1 does not interact with T2 or troponin I but does interact weakly with the NH2 terminus of tropomyosin and can be expected to bind weakly at the residual interaction site(s) at the COOH terminus of NPTM, the observed effects of T1 have been ascribed to the linking of neighboring NPTM molecules at their ends.
我们使用了一种不可聚合形式的原肌球蛋白（NPTM），在50 mM KCl ± Ca2+条件下，研究了肌钙蛋白T的T1区域（残基1 - 158）和T2区域（残基159 - 259）与细肌丝其他组分之间的相互作用。在这些条件下，完整的肌钙蛋白（± Ca2+）能使NPTM与F - 肌动蛋白的结合完全恢复，并且在每种情况下，如Scatchard和Hill图所示，仍保留一定程度的协同性。单独的片段T2对NPTM与F - 肌动蛋白的相互作用有较小的诱导作用。在存在肌钙蛋白I的情况下，这种相互作用增强到超过单独任何一种组分所观察到的水平。肌钙蛋白C能适度地（-Ca2+）和显著地（+Ca2+）降低T2和肌钙蛋白I的作用。虽然单独的片段T1不促进诱导作用，但它会增强T2和肌钙蛋白I的作用。由于T1不与T2或肌钙蛋白I相互作用，但确实与原肌球蛋白的NH2末端弱相互作用，并且可以预期在NPTM的COOH末端的残余相互作用位点处弱结合，所以观察到的T1的作用归因于相邻NPTM分子在其末端的连接。
