| Modification Notes |
The cystatins comprise a superfamily of proteins that contain multiple cystatin-like sequences and may function as active cysteine protease inhibitors. Cystatin proteins are divided into three distinct subfamilies, designated type 1 cystatins (stefins), type 2 cystatins and kininogens. The type 2 cystatins are expressed in human fluids and secretions and are encoded by genes that localize to a cystatin locus on chromosome 20. Cystatin 11, also known as SC13 or CST8L, is a 138 amino acid protein that localizes to both the nucleus and the cytoplasm and belongs to the type 2 subfamily of cystatins. Detected in epididymal and epithelial tissue, cystatin 11 functions as an antibacterial protein that is thought to play a role in sperm maturation and fertilization. Multiple isoforms of cystatin 11 exist due to alternative splicing events. |