Part of prostatein which is the major secretory glycoprotein of ventral prostate gland. Steroid-binding protein; can bind non-polar steroids, cholesterol and a group of small proline-rich peptides. Prostatein is composed of three different peptides called C1, C2 and C3. These form covalent C1:C3 (F) and C2:C3 (S) heterodimers whose non-covalent association forms tetrameric (C1:C3/C3:C2) prostatein molecules. Highly expressed in ventral prostate. Androgen dependent, as shown by the decrease in the level of the protein following castration. Belongs to the secretoglobin family. Lipophilin subfamily.