Characterization of the Thyroxine-Binding Site of Thyroxine-Binding Globulin by Site-Directed Mutagenesis

Characterization of the thyroxine-binding site of thyroxine-binding globulin by site-directed mutagenesis.

The principal transport protein for T4 in human blood, thyroxine-binding globulin (TBG), binds T4 with an exceptionally high affinity (Ka = 10(10) M(-1)). Its homology to the superfamily of the serpins has recently been used in the design of chimeric proteins, providing experimental evidence that an eight-stranded beta-barrel domain encompasses the ligand-binding site. We have now characterized...

Thyroxine-Binding Globulin Concentrations

Plasma thyroid hormone concentrations may be abnormal in non-thyroid disease and pose diagnostic problems. For example, concentrations of triiodothyronine (T3) in the blood decline in acute illness with a reciprocal increase in reverse triiodothyronine (reverse T3), but thyroxine (T4) concentrations are usually normal or only slightly decreased (1, 2). However, McLarty et al. (3) reported that ...

Familial thyroxine-binding globulin deficiency.

Genetically determined thyroxine-binding globulin deficiency is described in two families in the United Kingdom. All subjects in both pedigrees were euthyroid. Transmission was by sex-linkage; males showed low serum protein bound iodine and high thyroxine (T4) resin uptake due to complete absence of serum thryroxine-binding globulin; females were less severely affected. The distinctive biochemi...

Thyroxine-binding globulin, hyperthyroxinemia and hepatocellular carcinoma.

Studies on Human Thyroxine - Binding Globulin

to large volumes of serum may be due to adsorption of neuraminidases to the Sepharose either directly from serum or as the result of bacterial contamination. Partial desialylation of TBG in vivo may be an early step in the catabolism of this protein.