Related Experiment Video
Updated: Aug 5, 2026

Biochemical Reconstitution of Steroid Receptor•Hsp90 Protein Complexes and Reactivation of Ligand Binding
Published on: September 21, 2011
Physiologic properties of steroid hormone-binding proteins in avian blood
Abstract:
The physiologic properties of steroid hormone-binding proteins have been partially characterized in plasmas of 23 avian species (8 orders and 12 families). A specific sex hormone-binding protein (SBP) with high affinity and low capacity, as found in amphibians and some reptiles and mammals, could not be identified in any of the avian species investigated. In addition SBP appeared to be totally absent in the blood of posthatching and juvenile stages of two species, and in the embryonic blood of three species. For birds it is concluded that sex steroid hormones circulate bound to plasma albumins with low affinity (Kd = 10(-5) mol/liter) and very high capacity. There are two protein-binding systems for corticosterone in the blood of all species investigated, including samples collected from embryos. One is saturable and specific with low capacity (10(-8) -10(-9) mol/liter) and high affinity (Kd = 10(-7) -10(-9) mol/liter), whereas the other is a nonspecific component with very high capacity and low affinity (Kd = 10(-5) mol/liter). Specificity studies show that the high-affinity binding system for corticosterone also binds progesterone with virtually identical affinity, whereas testosterone and estradiol are bound with lower affinity. These data suggest that the high-affinity binding protein in avian blood has physiologic properties similar to mammalian corticosteroid-binding globulin (CBP).
Related Concept Videos
Intracellular Hormone Receptors
Internal Receptors
Drug Distribution: Plasma Protein Binding
Drug Binding to Blood Components
HSA is the most abundant plasma protein and is vital in drug binding. It contains distinct drug-binding sites, with different drugs exhibiting affinity for specific sites. There are three main drug-binding domains for HSA: sites I, II, and III. These domains are further...
Factors Affecting Protein-Drug Binding: Drug-Related Factors
One crucial factor in drug-protein binding is the drug's lipophilicity or its affinity for fat. More lipophilic drugs tend to have higher binding extents. For example, highly lipophilic drugs like cloxacillin exhibit substantial protein binding, with as much as 95% of the drug binding to proteins. In contrast,...
Factors Affecting Protein-Drug Binding: Protein-Related Factors
The physicochemical properties of a drug play a significant role in its ability to bind to proteins. Lipophilic drugs, which dissolve in fats, oils, and lipids, can be bound by...

