A novel NADPH-dependent cytosolic 3,5,3'-triiodo-L-thyronine-binding protein (CTBP; 5.1S) in rat liver: a comparison with 4.7S NADPH-dependent CTBP.
A novel NADPH-dependent cytosolic 3,5,3'-triiodo-L-thyronine-binding protein (CTBP; 5.1S) in rat liver: a comparison with 4.7S NADPH-dependent CTBP.
复制标题
大鼠肝脏中新型 NADPH 依赖性胞质 3,5,3-三碘-L-甲状腺氨酸结合蛋白（CTBP；5.1S）：与 4.7S NADPH 依赖性 CTBP 的比较。
DOI：
10.1210/endo-129-4-1701
复制
发表时间：
1991
期刊：
影响因子：
4.8
通讯作者：
T. Takeda
中科院分区：
文献类型：
--
作者：
M. Kobayashi;K. Hashizume;S. Suzuki;K. Ichikawa;T. Takeda
用Q-Sepharose、Phenyl-Sepharose、Red-Sepharose和聚丙烯酰胺凝胶电泳从大鼠肝胞浆中分离纯化了一种新的NADPH依赖的胞浆3，5，3 '-三碘-L-甲状腺原氨酸（T3）结合蛋白（CTBP）。CTBP的沉降系数为5.1S，斯托克斯半径为35 A，计算的摩尔重量为76，000。表面上均质的蛋白质由多肽链的二聚体组成，通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳估计分子量为38，000。NADPH增加5.1S CTBP对T3的亲和力和最大结合容量。3.0 × 10（-8）M NADPH可获得与T3结合的最大活性。计算的最大亲和常数为2.4 × 10（9）M-1，最大结合容量为21，000 pmol T3/mg 5.1S CTBP。碘甲腺原氨酸类似物对5.1S CTBP的亲和力顺序如下：D-T3大于L-T3大于L-T4大于三碘甲腺乙酸。T3结合的最适pH为7.2-7.5。Ca 2+、Mg 2+和Mn 2+（0.1-10 mM）不影响T3与CTBP的结合。Zn ~（2+）（1.0 mM）则抑制这种结合。这些结果表明，大鼠肝脏中存在5.1S NADPH依赖性CTBP，其与我们实验室从大鼠肾脏中纯化的4.7S CTBP不同。
A novel NADPH-dependent cytosolic 3,5,3'-triiodo-L-thyronine (T3)-binding protein (CTBP) was purified by sequential fractionation of rat liver cytosol on Q-Sepharose, phenyl-Sepharose, red-Sepharose, and polyacrylamide gel electrophoresis under nondenaturing conditions. The CTBP had a sedimentation coefficient of 5.1S, a Stokes' radius of 35 A, and a calculated mol wt of 76,000. The apparently homogenous protein consisted of a dimer of a polypeptide chain with a mol wt of 38,000 as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. NADPH increased both the affinity and maximal binding capacity for T3 in the 5.1S CTBP. The maximal activity to bind T3 was obtained by 3.0 x 10(-8) M NADPH. The calculated maximal affinity constant was 2.4 x 10(9) M-1, and the maximal binding capacity was 21,000 pmol T3/mg 5.1S CTBP. The order of affinity of iodothyronine analogs to the 5.1S CTBP was as follows: D-T3 greater than L-T3 greater than L-T4 greater than triiodothyroacetic acid. The optimal pH for T3 binding was 7.2-7.5. Ca2+, Mg2+, and Mn2+ (0.1-10 mM) did not influence T3 binding to CTBP. Zn2+ (1.0 mM), however, inhibited the binding. These results suggested that 5.1S NADPH-dependent CTBP, which is distinct from 4.7S CTBP that had been purified in our laboratory from rat kidney, is present in rat liver.