U-box domain, a modified RING finger, found in peptidyl-prolyl cis-trans isomerase-like 2 (PPIL2) and similar proteins
PPIL2 (EC 5.2.1.8), also known as PPIase, CYC4, cyclophilin-60 (Cyp60), cyclophilin-like protein Cyp-60, or Rotamase PPIL2, is a nuclear-specific cyclophilin which interacts with the proteinase inhibitor eglin c and regulates gene expression. PPIL2 belongs to the cyclophilin family of peptidylprolyl isomerases and catalyzes cis-trans isomerization of proline-peptide bonds, which is often a rate-limiting step in protein folding. It positively regulates beta-site amyloid precursor protein cleaving enzyme (BACE1) expression and beta-secretase activity. Moreover, PPIL2 plays an important role in the translocation of CD147 to the cell surface, and thus may present a novel target for therapeutic interventions in diseases where CD147 functions as a pathogenic factor in cancer, human immunodeficiency virus infection, or rheumatoid arthritis. PPIL2 contains an N-terminal RING-like U-box domain and a C-terminal cyclophilin (Cyp)-like chaperone domain.
Jiyao W et al.(2023). "The conserved domain database in 2023.",