early lactation protein (ELP), colostrum trypsin inhibitor (CTI), and similar proteins
This model includes the Kunitz-type proteins, colostrum trypsin inhibitor (CTI, also called colostrum BPI) and early lactation protein (ELP). In marsupials, the ELP gene is expressed in the mammary gland and the protein is secreted into milk during early lactation. Mature ELP shares approximately 55.4% similarity with the colostrum-specific bovine CTI protein. Marsupial ELP and eutherian CTI both have a single Kunitz domain and are secreted only during the early lactation phases, suggesting that this protein may have an important role in the immunologically immature young of these species. These proteins are similar to Kunitz-type proteinase inhibitors such as BPTI (bovine pancreatic trypsin inhibitor) that shows an alpha/beta fold with irregular secondary structure stabilized by three disulfide bonds.
Jiyao W et al.(2023). "The conserved domain database in 2023.",