Corticosteroid binding globulin, testosterone-estradiol binding globulin, and androgen binding protein belong to protein families distinct from steroid receptors.
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Bardin CW, Gunsalus GL, Musto NA, Cheng CY, Reventos J, Smith C, Underhill DA, Hammond G
Corticosteroid binding globulin, testosterone-estradiol binding globulin, and androgen binding protein belong to protein families distinct from steroid receptors.
J Steroid Biochem. 1988;30(1-6):131-9.
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- 3386241 [ View in PubMed]
- Abstract
The cDNA nucleotide sequences and the deduced amino acid sequences of human corticosteroid binding globulin (hCBG), human testosterone-estradiol binding globulin (hTeBG), and rat androgen binding protein (rABP) were determined. Studies of the steroid binding sites suggest they are toward the carboxy-terminus in hTeBG and rABP and more central in hCBG. hCBG has remarkable sequence homology with members of a superfamily whose functions have diverged; these include thyroxine-binding protein, serine protease inhibitors, egg white proteins, and angiotensinogen. hTeBG and rABP have a 68% amino acid sequence identity. Hybridization studies suggest that hTeBG is probably even more closely related, if not identical, to hABP. The carboxy-terminal sequences of hTeBG and rABP are also similar to that of protein S, a vitamin-K-dependent clotting factor. There were no nucleotide or amino acid sequence homologies between hCBG, hTeBG, or rABP and other steroid binding proteins such as steroid receptors, albumin, alpha-fetoprotein, and vitamin D binding protein. We conclude that the "extracellular steroid binding proteins" and steroid receptors do not appear to have descended from a common ancestor.