Fanjul A N, Farias R N
Departamento de Bioquimica de la Nutrición, Instituto Superior de Investigaciones Biológicas, Consejo de Investigaciones Cientificas y Técnicas-Universidad Nacional de Tucuman, Argentina.
J Biol Chem. 1991 Sep 5;266(25):16415-9.
Four cytosolic 3,5,3'-triiodo-L-thyronine-binding proteins (CTBP) were isolated from hemoglobin-free human erythrocyte on DEAE-cellulose column by linear gradient of NaCl (0-0.4 M). CTBP I, II, and IV underwent rapid loss of their activities at low temperatures, whereas CTBP III was cold-insensitive. Reactivation of cold-inactivated CTBPs by warming was obtained at 20 and 37 degrees C. CTBP I, II, and IV were not inhibited by thiol-blocking agents, whereas CTBP III was blocked. Scatchard analysis of L-3,5,3'-triodo-thyronine binding showed a high affinity site with Kd on the order of 10(-10) M for CTBP II and Kd values of about 10(-9) M for CTBP I and IV and of about 10(-8) M for CTBP III. The order of affinity of iodothyronine analogues to CTBPs was similar in CTBP I, II, and IV but different in CTBP III. Chromatography on Sephacryl S-200 HR showed the elution of a single peak for each CTBP. The apparent molecular weights were about 200,000, 200,000, 25,000, and 60,000 for CTBP I, II, III, and IV, respectively. The physiological relevance of these CTBPs is discussed.
通过NaCl（0-0.4M）线性梯度在DEAE-纤维素柱上从无血红蛋白的人红细胞中分离出四种胞质3,5,3'-三碘-L-甲状腺原氨酸结合蛋白（CTBP）。CTBP I、II和IV在低温下其活性迅速丧失，而CTBP III对冷不敏感。在20℃和37℃下通过升温可使冷失活的CTBP重新激活。CTBP I、II和IV不受硫醇阻断剂的抑制，而CTBP III被阻断。对L-3,5,3'-三碘甲状腺原氨酸结合的Scatchard分析表明，CTBP II有一个Kd约为10^(-10)M的高亲和力位点，CTBP I和IV的Kd值约为10^(-9)M，CTBP III的Kd值约为10^(-8)M。碘甲状腺原氨酸类似物与CTBP的亲和力顺序在CTBP I、II和IV中相似，但在CTBP III中不同。在Sephacryl S-200 HR上进行色谱分析，每个CTBP均洗脱为单峰。CTBP I、II、III和IV的表观分子量分别约为200,000、200,000、25,000和60,000。讨论了这些CTBP的生理相关性。
