This family consists of the mammalian specific protein beta-microseminoprotein. Prostatic secretory protein of 94 amino acids (PSP94), also called beta-microseminoprotein, is a small, nonglycosylated protein, rich in cysteine residues. It was first isolated as a major protein from human seminal plasma [1]. The exact function of this protein is unknown.

1: PSP94 (or beta-microseminoprotein) is a secretory protein specifically expressed and synthesized in the lateral lobe of the rat prostate . Kwong J, Xuan JW, Choi HL, Chan PS, Chan FL; Prostate 2000;42:219-229. PMID:10639193