InterPro domain: IPR000555

This domain is known as the MPN domain [ 1 ], PAD-1-like domain [ 2 ], JABP1 domain [ 3 ] or JAMM domain [ 4 ]. Proteins with this domain include proteasome regulatory subunits, eukaryotic initiation factor 3 (eIF3) subunits and regulators of transcription factors. They are metalloenzymes that function as the ubiquitin isopeptidase/deubiquitinase in the ubiquitin-based signaling and protein turnover pathways in eukaryotes [ 5 ]. Versions of the domain in prokaryotic cognates of the ubiquitin-modification pathway are predicted to have a similar role [ 5 ].

The archaeal (H. volcanii) JAMM domain containing protein, HvJAMM1, cleaves ubiquitin-like small archaeal modifier proteins (SAMP1/2) from protein conjugates [ 6 ]. The bacterial JAMM domain containing protein QbsD from Pseudomonas fluorescens cleaves the C-terminal amino acid residues of the sulfur carrier protein QbsE prior to the formation of the carboxy-terminal thiocarboxylate [ 7 ].

1. The PCI domain: a common theme in three multiprotein complexes. Trends Biochem. Sci. 23, 204-5
2. Eukaryotic signalling domain homologues in archaea and bacteria. Ancient ancestry and horizontal gene transfer. J. Mol. Biol. 289, 729-45
3. A global census of fission yeast deubiquitinating enzyme localization and interaction networks reveals distinct compartmentalization profiles and overlapping functions in endocytosis and polarity. PLoS Biol. 8, 611-5
4. Role of Rpn11 metalloprotease in deubiquitination and degradation by the 26S proteasome. Science 298, 971-87
5. The prokaryotic antecedents of the ubiquitin-signaling system and the early evolution of ubiquitin-like beta-grasp domains. Genome Biol. 7, R60
6. Archaeal JAB1/MPN/MOV34 metalloenzyme (HvJAMM1) cleaves ubiquitin-like small archaeal modifier proteins (SAMPs) from protein-conjugates. Mol. Microbiol. 86, 2941-4
7. Biosynthesis of the thioquinolobactin siderophore: an interesting variation on sulfur transfer. J. Bacteriol. 189