Takamatsu J, Refetoff S
J Clin Endocrinol Metab. 1986 Nov;63(5):1140-4. doi: 10.1210/jcem-63-5-1140.
The five known types of inherited variant T4-binding globulin (TBG) have in common increased sensitivity to heat denaturation compared to the common type TBG (TBG-C). In the course of studies to screen for and characterize variant TBGs in population groups, we detected a unique TBG with marked resistance to heat denaturation. The propositus was a 22-year-old black man without personal or family history of thyroid disease. His native TBG (nTBG) in serum had a t1/2 of denaturation at 56 C of 90 min compared to a mean value of 6.8 +/- 1.1 (+/- SD) min for TBG-C. This variant TBG, termed TBG-Chicago, was also resistant to acid denaturation, but was indistinguishable from TBG-C in terms of immunoreactivity, microheterogeneity on isoelectric focusing, and affinity for T4. It had a single T4-binding site and a normal concentration in serum associated with iodothyronine levels within the normal range. The mode of inheritance of TBG-Chicago appears to be X-chromosome linked. The mother of the propositus was heterozygous; her serum contained approximately 40% TBG-Chicago and 60% of another variant TBG common in blacks, TBG-S. The father had TBG-C, a trait that was not transmitted to his son. The exact nature of this variant TBG is not known. It most likely represents a mutation in the polypeptide chain of the molecule with formation of stronger intramolecular bonds.
已知的五种遗传性变异甲状腺素结合球蛋白（TBG）与常见类型的TBG（TBG-C）相比，其共同特点是对热变性的敏感性增加。在对人群中变异TBG进行筛查和特征描述的研究过程中，我们检测到一种对热变性具有显著抗性的独特TBG。先证者是一名22岁的黑人男性，无甲状腺疾病的个人或家族史。他血清中的天然TBG（nTBG）在56℃下变性的半衰期为90分钟，而TBG-C的平均值为6.8±1.1（±标准差）分钟。这种变异TBG被称为TBG-芝加哥型，它也对酸变性具有抗性，但在免疫反应性、等电聚焦的微异质性以及对T4的亲和力方面与TBG-C没有区别。它有一个单一的T4结合位点，血清中浓度正常，与正常范围内的碘甲状腺原氨酸水平相关。TBG-芝加哥型的遗传方式似乎是X染色体连锁。先证者的母亲是杂合子；她的血清中约含40%的TBG-芝加哥型和60%的另一种在黑人中常见的变异TBG，即TBG-S。父亲有TBG-C，该性状未遗传给儿子。这种变异TBG的确切性质尚不清楚。它很可能代表分子多肽链中的一种突变，形成了更强的分子内键。
