Cystatin F, also known as leukocystatin and CMAP (Cystatin-like Metastasis-Associated Protein), is a new member of the Cystatin superfamily (1-3). Cystatin F is selectively expressed by hematopoietic cells and may be a biomarker for both liver metastasis and inflammatory lung disorders (3, 4). As a cysteine protease inhibitor, it shows selectivity towards Cathepsin L and legumain (1, 2, 5). Compared to other secreted Cystatins including C, D, E/M, S, SA and SN, which contain two intrachain disulfide bonds, Cystatin F has two extra Cys residues that may be involved in interchain disulfide bonds. rmCystatin F and rhCystatin F exhibit disulfide bond-linked dimer formation, which was also the case for an E. coli expressed fusion protein containing mature human Cystatin F and glutathione S-transferase (2). Recombinant protein corresponding to Ala19-Gln144 from mouse Cystatin F, fused to 6-His-Tag at C-terminal, expressed in NS0 cells. Uniprot/Swiss Accession: O89098 Molecular Weight: Calculated molecular mass of 15kD and migrates as a 20kD band in SDS-PAGE under reducing conditions. Activity: Measured by its ability to inhibit active Cathepsin L cleavage of a fluorogenic peptide substrate Z-LR-AMC. The IC50 value is <60 nM, as measured under the described conditions. Storage and Stability: May be stored at 4C for short-term only. Aliquot to avoid repeated freezing and thawing. Store at -20C. Aliquots are stable for 6 months after receipt at -20C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.
