CSTB, also known as Cystatin B is an anti-protease implicated in myoclonus epilepsy, a degenerative disease of the central nervous system. The cystatin superfamily encompasses proteins that contain multiple cystatin- like sequences. Some of the members are active cysteine protease inhibitors, while others have lost or perhaps never acquired this inhibitory activity. This protein is able to form a dimer stabilized by noncovalent forces and is thought to play a role in protecting against the proteases leaking from lysosomes. In cells, CSTB is located in the lysosomes and the cytoplasm, but also in the nucleus. Source: Recombinant protein corresponding to aa1-98 from human CSTB, fused to His-tag expressed in E. coli. Molecular Weight: ~13kD (118aa) Biological Activity: The IC50 value is <3nM. The inhibitory function of Cystatin B on protease activity of papain was measured by a fluorometric assay using Z-FR-AMC at pH 7.5 at 25C. Amino Acid Sequence: MGSSHHHHHH SSGLVPRGSH MMCGAPSATQ PATAETQHIA DQVRSQLEEK ENKKFPVFKA VSFKSQVVAG TNYFIKVHVG DEDFVHLRVF QSLPHENKPL TLSNYQTNKA KHDELTYF 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.
