Anti-H2B clustered histone 21 antibodies are used for the immunodetection of the protein encoded by the H2BC21 gene. In humans, the canonical protein has a reported length of 126 amino acid residues and a mass of 13.9 kDa. Its subcellular localization is in the nucleus and chromosomes. A member of the Histone H2B protein family, it is an important component of nucleosome. Post-translational modifications have been described, including glycosylation, ubiquitination and phosphorylation. Other names for this target antigen include H2B, H2B-GL105, H2B.1, H2BE, H2BFQ, H2BGL105, H2BQ, and GL105. Gene orthologs have been identified in the mouse, rat, bovine and chimpanzee species.