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whey acidic protein-type four-disulfide core domains. Members of the family include whey acidic protein, elafin (elastase-specific inhibitor), caltrin-like protein (a calcium transport inhibitor) and other extracellular proteinase inhibitors. A group of proteins containing 8 characteristically-spaced cysteine residuesforming disulphide bonds, have been termed '4-disulphide core' proteins. Protease inhibition occurs by insertion of the inhibitory loop into the active site pocket and interference with the catalytic residues of the protease.
Jiyao W et al.(2023). "The conserved domain database in 2023.",