PSMF1 is a protein that inhibits the activation of the proteasome by the 11S and 19S regulators. The 26S proteasome is a multicatalytic proteinase complex with a highly ordered structure composed of 2 complexes, a 20S core and a 19S regulator. The 20S core is composed of 4 rings of 28 non-identical subunits, 2 rings are composed of 7 alpha subunits and 2 rings are composed of 7 beta subunits. Recombinant human PSMF1 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography. Synonyms: Proteasome inhibitor subunit 1 isoform 1, PI31. NCBI no.: NP_006805