Modifications outside the proteinase binding loop in Cucurbita maxima trypsin inhibitor III (CMTI-III) analogues change the binding energy with bovine β-trypsin
- 2 October 1998
- journal article
- Published by Wiley in FEBS Letters
- Vol. 436 (2) , 174-178
- https://doi.org/10.1016/s0014-5793(98)01119-3
Abstract
Five 26-peptide analogues of the trypsin inhibitor [Pro 18 ]CMTI-III containing Leu or Tyr in position 7 and Val or Tyr in position 27: 1 (Leu 7 , Tyr 27 ), 2 (Tyr 7 , Val 27 ), 3 (Tyr 7 , Tyr 27 ), 4 (Leu 7 , Val 27 ) and 5 (Leu 7 , Ala 18 , Tyr 27 ) were synthesized by the solid-phase method. Analogues 1–4 displayed K a with bovine β-trypsin of the same order of magnitude as the wild CMTI-III inhibitor, whereas for analogue 5 , this value was lower by about 3 orders of magnitude. This indicated that for the analogues with Pro (but not with Ala) in position 18, the side-chain interactions between positions 7 and 27 did not play a critical role for the stabilization of the active structure. In addition, these results also suggest that Tyr 7 is involved in an additional aromatic interaction with position 41 of the enzyme.Keywords
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