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trypsin inhibitor-like cysteine rich domain TIL (trypsin inhibitor-like) cysteine rich domains are found in smapins (small serine proteinase inhibitor), or Ascaris trypsin inhibitor (ATI)-like proteins, whose members include anticoagulant proteins, elastase inhibitors, trypsin inhibitors, thrombin inhibitors, and chymotrypsin inhibitors. The TIL domain is also found in some large modular glycoproteins, including the von Willebrand factor (VWF), mucin-6, mucin-19, and SCO-spondin, among others. The TIL domain is characterized by the presence of five disulfide bonds (two of which are located on either side of the reactive site) in a single small protein domain of 61-62 residues. The cysteine residues that form the disulfide bonds are linked in the pattern: cysteines 1-7, 2-6, 3-5, 4-10 and 8-9. TILs can occur as a single domain or in multiple tandem arrangements. The disulfide bonds account for the unusual resistance to proteolysis and heat denaturation of these proteins. Smapins possess an unusual fold and, with the exception of the reactive site, shows no similarity to other serine protease inhibitors. The serine protease inhibitors comprise a large family of molecules involved in inflammatory responses, blood clotting, and complement activation. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",