Macrodomains are found in a variety of proteins with diverse cellular functions, as a stand-alone domain or in combination with other domains like in histone macroH2A and some PARPs (poly ADP-ribose polymerases). Macrodomains can recognize ADP-ribose (ADPr) in both its free and protein-linked forms, in related ligands, such as O-acyl-ADP-ribose (OAADPr), and even in ligands unrelated to ADPr. Members of this family are similar to macroH2A, a variant of the major-type core histone H2A, which contains an N-terminal H2A domain and a C-terminal nonhistone macrodomain. Histone macroH2A is enriched on the inactive X chromosome of mammalian female cells. It does not bind poly ADP-ribose, but does bind the monomeric SirT1 metabolite O-acetyl-ADP-ribose (OAADPR) with high affinity through its macrodomain. This family also includes the ADP-ribose binding macrodomain of the macroH2A variant, macroH2A1.1. The macroH2A1.1 isoform inhibits PARP1-dependent DNA-damage induced chromatin dynamics. The putative ADP-ribose binding pocket of the human macroH2A2 macrodomain exhibits marked structural differences compared with the macroH2A1.1 variant.
Jiyao W et al.(2023). "The conserved domain database in 2023.",