Homodimer; Interacts with PI16. Sperm surface. Strongly expressed in prostate, liver, kidney, breast and penis. Also expressed in pancreas, esophagus, stomach, deodenum, colon, trachea, lung, salivary glands and fallopian tube. PSP94 is expressed in lung and breast, whereas PSP57 is found in kidney and bladder. Disease susceptibility is associated with variants affecting the gene represented in this entry. Specific receptors for this protein are found on spermatozoa and in the prostate. Belongs to the beta-microseminoprotein family. Was originally thought to inhibit the secretion of FSH by pituitary cells.