Crystal structure of recombinant human stromal cell‐derived factor‐1α

Introduction.Chemokines are a superfamily of cytokine molecules that mediate several cellular functions.[1][2] The chemokines superfamily has been classified into three species, CC, CXC, and CX 3 C, based on the presence of an additional one or three amino acids between the first two cysteine residues.3 Stromal cell-derived factor-1a (SDF-1a) is an unusual member of the CXC family that was first isolated from a mouse bone marrow stromal cell line.4,5 SDF-1a has been implicated in a variety of physical functions, including hematopoiesis, cardiogenesis, B cell lymphopoiesis, and migration and cellular colonization of primordial germ cells in mammals.6-8 SDF-1a interacts specifically with the physiological receptor CXCR4 for multicellular functions.A knockout experiment of either the sdf-1a or cxcr4 gene supported the claim that the SDF-1a/CXCR4 complex has an important role in embryonic development and proliferation.5,9 Mice lacking the sdf-1a gene died in the perinatal period due to a severe cardiac ventricular system septum defect.5 Although various functions of SDF-1a have been reported, biochemical assays of its activity have been limited because the protein is not over-produced in a recombinant form.To overcome this obstacle, we expressed human SDF-1a in E. coli and obtained the refolded protein.The three-dimensional crystal structure of refolded SDF-1a displays some structural differences from previously reported structures.Also, the chemotaxis assay shows that refolded SDF-1a binds to receptors in the CCRF-CEM cell line, indicating that the refolded protein is an active form.