Kratzner, R.R.KratznerDebreczeni, J. E.J. E.DebreczeniPape, T.T.PapeSchneider, Thomas R.Thomas R.SchneiderWentzel, A.A.WentzelKolmar, HaraldHaraldKolmarSheldrick, George M.George M.SheldrickUson, I.I.Uson2018-11-072018-11-072005https://resolver.sub.uni-goettingen.de/purl?gro-2/49872The Ecballium elaterium trypsin inhibitor II (EETI-II) belongs to the family of squash inhibitors and is one of the strongest inhibitors known for trypsin. The eight independent molecules of EETI-II in the crystal structure reported here provide a good opportunity to test the hypothesis that this small cystine-knot protein (knottin) is sufficiently rigid to be used as a molecular scaffold for protein-engineering purposes. To extend this test, the structures of two complexes of EETI-II with trypsin have also been determined, one carrying a four-amino-acid mutation of EETI-II. The remarkable similarity of these structures confirms the rigidity of the molecular framework and hence its suitability as a molecular scaffold.journal_article10.1107/S090744490502120716131759000231243400011