Li Q, Yamamoto N, Morisawa S, Inoue A
Department of Biochemistry, Osaka City University Medical School, Japan.
J Cell Biochem. 1993 Apr;51(4):458-64. doi: 10.1002/jcb.2400510411.
Long-chain fatty acids and their acyl-CoA esters are potent inhibitors of nuclear thyroid hormone (T3) receptor in vitro. In the present study, we obtained evidence for acyl-CoA binding activity in the nuclear extract from rat liver. The activity sedimented at a position (3.5 S) identical with that of the T3 receptor, and the two activities sedimented together. Similarly, they coeluted on DEAE-Sephadex. After partial purification of the receptor, it was again inhibited strongly by acyl-CoAs. Heat stability and a partial trypsin digestion of the receptor both suggested that the action site of oleoyl-CoA overlapped the T3-binding domain of the receptor. In addition, thyroid hormone receptor beta 1, synthesized in vitro, bound oleoyl-CoA specifically and its T3-binding activity was inhibited. The dissociation constant for oleoyl-CoA binding to the partially purified receptor was 1.2 x 10(-7) M. This value as well as its molecular size distinguished the nuclear binding sites from the cytoplasmic fatty acid/acyl-CoA binding proteins. Oleoyl-CoA had no effect on the glucocorticoid receptor, another member of the nuclear hormone-receptor superfamily. From these results, we propose that thyroid hormone receptor is a specific acyl-CoA binding protein of the cell nucleus.
长链脂肪酸及其酰基辅酶A酯在体外是甲状腺激素（T3）核受体的有效抑制剂。在本研究中，我们获得了大鼠肝脏核提取物中酰基辅酶A结合活性的证据。该活性在与T3受体相同的位置（3.5 S）沉降，并且这两种活性一起沉降。同样，它们在DEAE-葡聚糖凝胶上共同洗脱。受体部分纯化后，再次受到酰基辅酶A的强烈抑制。受体的热稳定性和部分胰蛋白酶消化均表明油酰辅酶A的作用位点与受体的T3结合域重叠。此外，体外合成的甲状腺激素受体β1特异性结合油酰辅酶A，其T3结合活性受到抑制。油酰辅酶A与部分纯化受体结合的解离常数为1.2×10^(-7)。该值及其分子大小将核结合位点与细胞质脂肪酸/酰基辅酶A结合蛋白区分开来。油酰辅酶A对核激素受体超家族的另一个成员糖皮质激素受体没有影响。根据这些结果，我们提出甲状腺激素受体是细胞核的一种特异性酰基辅酶A结合蛋白。
