InterPro domain: IPR045128

PI31 is a regulatory subunit of the immunoproteasome which is an inhibitor of the 20S proteasome in vitro. PI31 is also an Fbxo7.Skp1 binding partner. Fbxo7 is an F-box protein, which are the substrate-recognition components of the Skp1-Cul1-F box protein (SCF) E3 ubiquitin ligases. The interaction between PI31 and Fbxo7.Skp1 occurs via the beta sheets of a N-terminal domain present in both proteins and known as FP(Fbxo7/PI31) domain. The structure of PI31 FP domain contains a novel alpha/beta-fold and two intermolecular contact surfaces [ 1 ].

1. Structure of a conserved dimerization domain within the F-box protein Fbxo7 and the PI31 proteasome inhibitor. J. Biol. Chem. 283, 22325-35