Permuted imelysin-like protein from Bacteroides ovatus (PIBO) and similar proteins
This family includes imelysin-like proteins such as imelysin-like protein from gut bacteria Bacteroides ovatus (PIBO) that have a circularly permuted topology compared with the canonical imelysin fold, such that the N-terminal and C-terminal regions are swapped in the primary sequence. PIBO is highly similar to imelysin-like protein from Psychrobacter arcticus (IPPA) despite low sequence similarity and circular permutation. PIBO is functionally equivalent to insulin-cleaving membrane protease (ICMP or imelysin), although the permutation results in the conserved GxHxxE motif to be at the C-terminus. It may have a conserved role in iron uptake although it adopts a structure distinctive from known metallopeptidases or iron-binding proteins.
Comment:The HxxE sequence motif is characteristic of M14 peptidases and is conserved in this family. However, the overall structure of this region differ from the known HxxE metallopeptidases, suggesting that imelysin-like proteins may not be peptidases.
Jiyao W et al.(2023). "The conserved domain database in 2023.",