Comparative structure analysis of proteinase inhibitors from the desert locust, Schistocerca gregaria

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The solution structure of three small serine proteinase inhibitors, two natural and one engineered protein, SGCI (Schistocerca gregaria chymotrypsin inhibitor), SGCI[L30R, K31M] and SGTI (Schistocerca gregaria trypsin inhibitor), were determined by homonuclear NMR-spectroscopy. The molecules exhibit different specificities towards target proteinases, where SGCI is a good chymotrypsin inhibitor, its mutant is a potent trypsin inhibitor, and SGTI inhibits both proteinases weakly. Interestingly, SGTI is a much better inhibitor of insect proteinases than of the mammalian ones used in common assays. All three molecules have a similar fold composed from three antiparallel β-pleated sheets with three disulfide bridges. The proteinase binding loop has a somewhat distinct geometry in all three peptides. Moreover, the stabilization of the structure is different in SGCI and SGTI. Proton-deuterium exchange experiments are indicative of a highly rigid core in SGTI but not in SGCI. We suggest that the observed structural properties play a significant role in the specificity of these inhibitors.

Original languageEnglish
Pages (from-to)527-537
Number of pages11
JournalEuropean Journal of Biochemistry
Issue number2
Publication statusPublished - Feb 16 2002


  • Flexibility
  • NMR structure
  • Serine proteinase inhibitor
  • Specificity

ASJC Scopus subject areas

  • Biochemistry

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