gamma-Glutamylcyclotransferase/CRF21: ProductsCRF21 (Cytochrome c-releasing factor 21; also C7orf24 or LOC79017) is a 21 kDa AIG2-like family member. It is a cytosolic protein that induces the release of Cytochrome c from mitochondria, possibly initiating apoptosis. Human CRF21 is 188 amino acids (aa) in length and is a complex of beta-sheets and alpha-helices that create two terminal domains. It has been proposed that CRF21 forms homodimers. There are at least two possible splice variants of human CRF21, one showing a 70 aa substitution, while the second variant shows an 18 aa substitution for aa 97-188. Full-length human CRF21 is 82% aa identical to mouse CRF21.