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macrodomain superfamily 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. Macrodomains include the yeast macrodomain Poa1 which is a phosphatase of ADP-ribose-1"-phosphate, a by-product of tRNA splicing. Some macrodomains have ADPr-unrelated binding partners such as the coronavirus SUD-N (N-terminal subdomain) and SUD-M (middle subdomain) of the SARS-unique domain (SUD) which bind G-quadruplexes (unusual nucleic-acid structures formed by consecutive guanosine nucleotides). Macrodomains regulate a wide variety of cellular and organismal processes, including DNA damage repair, signal transduction, and immune response.
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