Purified by chromatography. Stem cell factor / KIT ligand (SCF) is a cytokine which binds CD117 (c-Kit). SCF is also known as steel factor or c-kit ligand. SCF exists in two forms, cell surface bound SCF and soluble (or free) SCF. Soluble SCF is produced by the cleavage of surface bound SCF by metalloproteases. SCF is a growth factor important for the survival, proliferation and differentiation of hematopoietic stem cells and other hematopoietic progenitor cells. One of its roles is to change the BFU-E (burst-forming unit-erythroid) cells, which are the earliest erythrocyte precursors in the erythrocytic series, into the CFU-E (colony-forming unit-erythroid). Amino Acid Sequence: The sequence of the first five amino acids was determined to be Met-Glu-Gly-Ile-Cys Biological Activity: The ED50 as determined by the dose-dependent stimulation of Human TF-1 cells is <2ng/ml, corresponding to a Specific Activity of 5x10e5IU/mg.