| Serpins are inhibitors of serine proteases that act by reacting covalently, leaving a segment attached to the protease, and then the remaining segment dissociates and rearranges itself into a new conformation. |
| Trypsin is primarily a beta-sheet protein. After a few seconds the active site residues become highlighted in cyan. |
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PDB (1dpo) Earnest, T., Fauman, E., Craik, C.S., Stroud, R. A structure of trypsin at 120 K: comparison of low temperature and room temperature structures. Proteins v10 pp.171-187, 1991 PubMed |
| Trypsin with its anti-trypsin bound. The thick blue segment of the anti-trypsin (serpin) has entered the catalytic site of trypsin, and will eventually be cleaved, leaving an acyl-enzyme intermediate. Notice the 4-stranded beta-sheet colored cyan. |
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PDB (1k9o) Ye, S., Cech, A.L., Belmares, R., Bergstrom, R.C., Tong, Y., Corey, D.R., Kanost, M.R., Goldsmith, E.J. The structure of a Michaelis serpin-protease complex. Nat.Struct.Biol. v8 pp.979-983 , 2001 (PubMed) |
| The serpin anti-trypsin after being cleaved by trypsin. Notice that the blue segment has now formed as a beta-strand and inserted itself into the 4-stranded sheet. |
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PDB (9api) Engh, R., Lobermann, H., Schneider, M., Wiegand, G., Huber, R., Laurell, C.B. The S variant of human alpha 1-antitrypsin, structure and implications for function and metabolism. Protein Eng. v2 pp.407-415 , 1989 (PubMed) |