ABSTRACT
The steroid hormones directly involved in the control of reproduction are estradiol, progesterone, and testosterone. Steroid hormone receptors are intracellular soluble proteins. Steroid hormone receptors are also phosphoproteins, where serine and threonine residues are phosphorylated, and eventually tyrosine residues. Steroid hormone receptors are extremely sensitive to the actions of proteases endogenous to tissue extracts. Phosphorylation of defined amino acids might be necessary for the transactivation function of steroid receptors. The large scale purification of steroid receptors by either purification procedure is very difficult due to their low concentrations in the organs of origin. Sparse reports describe membrane proteins that specifically bind steroid hormones. As the steroid hormone receptors are large proteins, it has generally been necessary to orientate overlapping clones, in order to get the complete reading frame of the protein. Steroid hormones were given to experimental animals. This approach was unable to provide very accurate information about the hormonal regulation of sex steroid receptors.
