| Macro | |||||||||
|---|---|---|---|---|---|---|---|---|---|
|   Crystal structure of the macro-domain of human core histone variant macroh2a1.1  | |||||||||
| Identifiers | |||||||||
| Symbol | Macro | ||||||||
| Pfam | PF01661 | ||||||||
| Pfam clan | CL0223 | ||||||||
| InterPro | IPR002589 | ||||||||
| SCOP2 | 1vhu / SCOPe / SUPFAM | ||||||||
| CDD | cd02749 | ||||||||
  | |||||||||
In molecular biology, the Macro domain (often also written macrodomain) or A1pp domain is an ancient, evolutionary conserved structural module found in all kingdoms of life as well as some viruses. [1] Macro domains are modules of about 180 amino acids that can bind ADP-ribose, an NAD metabolite, or related ligands. Binding to ADP-ribose can be either covalent or non-covalent: [2] in certain cases it is believed to bind non-covalently, [3] while in other cases (such as Aprataxin) it appears to bind both non-covalently through a zinc finger motif, and covalently through a separate region of the protein. [4]
The domain was described originally in association with the ADP-ribose 1-phosphate (Appr-1-P)-processing activity (A1pp) of the yeast YBR022W protein and called A1pp. [5] However, the domain has been renamed Macro as it is the C-terminal domain of mammalian core histone macro-H2A. [6] [7] Macro domain proteins can be found in eukaryotes, in (mostly pathogenic) bacteria, in archaea and in ssRNA viruses, such as coronaviruses, Rubella and Hepatitis E viruses. In vertebrates the domain occurs in e.g. histone macroH2A, predicted poly-ADP-ribose polymerases (PARPs) and B aggressive lymphoma (BAL) protein. Zinc-containing macro domains (Zn-Macros) are primarily encountered in pathogenic microorganisms and have structurally distinct features from other macro domains, which include their function being strictly dependent on a catalytic zinc within the active site. [8] [9]
ADP-ribosylation of proteins is an important post-translational modification that occurs in a variety of biological processes, including DNA repair, regulation of transcription, chromatin biology, maintenance of genomic stability, telomere dynamics, [10] cell differentiation and proliferation, [11] necrosis and apoptosis, [12] and long-term memory formation. [13] The Macro domain recognises the ADP-ribose nucleotide and in some cases poly-ADP-ribose, and is thus a high-affinity ADP-ribose-binding module found in a number of otherwise unrelated proteins. [14]
ADP-ribosylation of DNA is relatively uncommon and has only been described for a small number of toxins that include pierisin, [15] scabin [16] and DarT. [17] [18] The Macro domain from the antitoxin DarG of the toxin-antitoxin system DarTG, both binds and removes the ADP-ribose modification added to DNA by the toxin DarT. [17] [18] The Macro domain from human, macroH2A1.1, binds an NAD metabolite O-acetyl-ADP-ribose. [19]
| Class | Subclass | Species | Activity | 
|---|---|---|---|
| MacroH2A-like | e | ADP-ribose binding | |
| MacroD-type | 'classic' | a, b, e, v | ADP-ribosyl bond hydrolysis | 
| Zn-dependent | b, e | ADP-ribosyl bond hydrolysis | |
| GDAP2-like | e | ADP-ribose binding | |
| ALC1-like | b, e | ADP-ribose binding or ADP-ribosyl bond hydrolysis | |
| PARG-like | PARG_cat | e | ADP-ribosyl bond hydrolysis | 
| mPARG (DUF2263) | b, e, v | ADP-ribosyl bond hydrolysis | |
| Macro2-type | e, v | ADP-ribosyl bond hydrolysis | |
| SUD-M-like | v | RNA binding | |
| DUF2362 | e | unknown | |
| a, Archaea; b, Bacteria; e, Eukarya; v, Virus | |||
The 3D structure of the Macro domain describes a mixed alpha/beta fold of a mixed beta sheet sandwiched between four helices with the ligand-binding pocket lies within the fold. [14] Several Macro domain-only domains are shorter than the structure of AF1521 and lack either the first strand or the C-terminal helix 5. Well conserved residues form a hydrophobic cleft and cluster around the AF1521-ADP-ribose binding site. [7] [14] [19] [20]