Prostatic steroid binding protein: gene duplication and steroid binding.

Abstract

The principal secretory protein in rat prostatic fluid is a steroid binding protein1–6 whose expression is stimulated by androgenic steroids7,8. This prostatic steroid binding protein is oligomeric, consisting of two subunits, one containing the polypeptides C1 and C3 and the other containing C2 and C39. We have isolated cDNA clones specific for each of the mRNAs which code for prostatic binding protein and note here the considerable DNA sequence homology between C1 and C2. Therefore, it is likely that duplication of an ancestral gene occurred and the subsequent divergence results in the expression of two related polypeptides that form part of a single protein. Furthermore, in view of the structure of the protein it is possible that the divergence of one of the genes has resulted in the capacity of this prostatic protein to bind steroids.