Protease, Serine 53 (PRSS53)

POL3S contains a signal peptide and 2 serine protease domains (Spd1 and Spd2), which have a number of cysteine residues predicted to form disulfide bonds. The Spd1 and Spd2 domains share between 32 and 40% sequence identity with those in other serine proteases, including PRSS36, and POL3S shares 81% and 80% identity with mouse and rat Pol3s, respectively. Western blot analysis showed that POL3S may form active dimers stabilized by disulfide bridges. Northern blot analysis detected expression of a 7.5-kb transcript in adult human liver, heart, testis, ovary, intestine, colon, and leukocytes as well as fetal kidney, liver, lung, and brain and several cancer cell lines. Shorter transcripts of 5.2 kb and 4.2 kb found in placenta, testis, and HeLa and lymphoblastic leukemia cells suggested alternative splicing.