Human HtrA3 protease, which induces mitochondria-mediated apoptosis, can be a tumor suppressor and a potential therapeutic target in the treatment of cancer. It may also have a role in ovarian development, granulosa cell differentiation and luteinization. The long isoform, HTRA3L, contains 453 amino acids and has a predicted molecular mass of 49 kD. It contains an N-terminal signal peptide, followed by an insulin/IGF (see 147440)-binding domain, a Kazal-type S protease inhibitor domain, a trypsin protease domain, and a PDZ domain. The short isoform, HTRA3S, contains 357 amino acids and has a predicted molecular mass of 38 kD.