Histone H2A.Z, also known as H2AFZ, is a member of the histone H2A family. Histones are basic nuclear proteins that are responsible for the nucleosome structure of the chromosomal fiber in eukaryotes. Nucleosomes consist of approximately 146 bp of DNA wrapped around a histone octamer composed of pairs of each of the four core histones (H2A, H2B, H3, and H4). H2AFZ may be involved in the formation of constitutive heterochromatin and may be required for chromosome segregation during cell division. Also, H2AFZ is a variant Histone H2A which replaces conventional H2A in a subset of nucleosomes. Recombinant human H2AFZ protein, fused to His-tag at N-terminus, was expressed in E.coli.