The PCI (for Proteasome, COP9, Initiation factor 3) domain (sometimes also referred to as the PINT domain, for Proteasome subunits, Int-6, Nip-1, and Trip-15) is present in six different subunits of 26 proteasome lid, COP9 signalosome (CSN) and eukaryotic translation initiation factor-3 (eIF3) complexes, as well as in subunits of certain other multiprotein complexes. The PCI domain mediates and … expand

The PCI (for Proteasome, COP9, Initiation factor 3) domain (sometimes also referred to as the PINT domain, for Proteasome subunits, Int-6, Nip-1, and Trip-15) is present in six different subunits of 26 proteasome lid, COP9 signalosome (CSN) and eukaryotic translation initiation factor-3 (eIF3) complexes, as well as in subunits of certain other multiprotein complexes. The PCI domain mediates and stabilizes protein-protein interactions within the complexes. The role of the PCI domains is most likely that of a scaffold for the other complex subunits and other binding partners. The PCI domain could play a role as a universal binding domain supporting intra-complex interactions as well as recruitments of additional ligands [ PUBMED:9644972 PUBMED:9605331 PUBMED:15790418 PUBMED:23818606 PUBMED:15180986 PUBMED:18854373 ].

PCI is an ~190-amino acid domain, not well conserved in its primary sequence, usually located near the C terminus of the protein. It does not contain any invariant residues or any conserved pattern of charged residues that would suggest a catalytic activity. The PCI domain is comprised of two subdomains that are intimately connected, an N-terminal helical bundle (HB) subdomain and a C-terminal globular winged helix (WH) subdomain. The C- terminal half of the PCI domain is much better conserved than the N-terminal half [ PUBMED:23818606 PUBMED:15180986 PUBMED:18854373 ].