Anti-H2AC21 antibodies are used in the immunodetection of the protein H2A clustered histone 21. In humans, the canonical protein has a reported length of 130 amino acid residues and a mass of 14 kDa. Its subcellular localization is in the nucleus and chromosomes. It is notably widely expressed in many tissue types. A member of the Histone H2A protein family, H2AC21 is an important component of nucleosome. Post-translational modifications have been described, including ubiquitination, acetylation and phosphorylation. Synonyms for this target antigen include histone 2, H2ab, histone cluster 2 H2A family member b, histone cluster 2, H2ab, and histone H2A type 2-B. H2AC21 gene orthologs have been reported in the mouse, rat, bovine and chimpanzee species.