PSP94, also known as b-microseminoprotein (b-MSP), is a secreted, non-glycosylated 16kD major protein in semen. It is highly expressed in prostate and numerous other tissues. In human blood plasma and seminal plasma, PSP94 binds to CRISP3 and PSPBP (also known as PI16), which are SCP domain containing proteins. A splice variant of PSP94, called PSP57, contains a 41 residue substitution for residues 37-77 in PSP94. Mature human PSP94 shares 44%, 53% and 79% aa sequence homology with mouse, porcine and baboon PSP94, respectively.