Human matriptase, encoded by the ST14 (suppression of tumorogenicity 14) gene, is also known as tumor associated differentially expressed gene 15 protein/TADG15) and membrane-type serine protease 1/MTSP1 (1). Predicted to have a significant role in tumor biology, matriptase may be a novel target for anticancer therapy (2). However, expressed in most human epithelia, matriptase is also important in several physiological processes (1). For example, it activates prostasin to initiate a protease cascade that is essential for epidermal differentiation (3), and it converts a single chain IGFBPrp1 into the twochain form (4). Matriptase is a type II transmembrane serine protease with a complex modular structure (1). The 855 amino acid (aa) sequence of human matriptase consists of a cytoplasmic tail (aa 155), a transmembrane domain (aa 56-76), and an extracellular portion (aa 77-55). The latter contains the following domains: SEA (aa 86-201), two CUBs (aa 214-334 and 340-47), four LDLRAs (aa 452-486, 487-523, 524-560, and 566-603), and a serine protease (aa 615-855). The physiological activation of the single chain zymogen requires the cleavage at the SEA domain within the ER or Golgi, association with HAI1, which facilitates the transport of the protease to the cell surface, and autocleavage at QARV(615)VGG (1). The activated matriptase is inhibited by HAI1, and the resulting HAI1 complex can be shed from the cell surface (1). Description: E. coli-derived recombinant protein corresponding to the sequence Gly596-Val855 of human Matriptase/ST14 protein (NCBI Accession NP_068813), with an N-terminal Met and 6-His tag. This protein corresponds to the catalytic domain, and is inhibited effectively by rhHAI1 and rhHAI2A. The protein was purified, auto-activated and further purified. Activity: Measured by its ability to cleave the fluorogenic peptide substrate Boc-QAR-AMC. Specific Activity: 10,000pmoles/min/ug, as measured under the described conditions. See Activity Assay Protocol. Molecular Mass: Predicted: 26kD. Observed (by SDS-PAGE, reducing conditions): 27kD (major) and minor autoactivation fragments Storage and Stability: Aliquot to avoid repeated freezing and thawing and store at -70C. Aliquots are stable for 6 months after receipt. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap.
