CCAAT/enhancer binding protein(C/EBP) α is a family of transcription factors that all contain a highly conserved, basic-leucine zipper domain at the C-terminus that is involved in dimerization and DNA binding. C/EBP family of transcription factors regulates viral and cellular CCAAT/enhancer element-mediated transcription. C/EBP family consist of several related proteins, C/EBP α, β,γ,δ, that form homodimers and that form heterodimers with each other. C/EBP proteins contain the bZIP region, which is characterized by two motifs in the C-terminal half of the protein; a basic region involved in DNA binding and a leucine zipper motif involved in dimerization. C/EBPs differ significantly in their physiological functions and in their downstream target genes. For example, mice lacking C/EBPα die shortly after birth due to severe hypoglycemia and the absence of glycogen storage in liver, whereas knockout of C/EBPβ causes defects in female reproduction. The bZip region of CEBP-α (residues 270-358) was produced in E.coli and purified by ion-exchange chromatography and FPLC gel-filtration chromatography.