Jaśkiewicz A, Lis K, Rózycki J, Kupryszewski G, Rolka K, Ragnarsson U, Zbyryt T, Wilusz T. Modifications outside the proteinase binding loop in Cucurbita maxima trypsin inhibitor III (CMTI-III) analogues change the binding energy with bovine beta-trypsin.
FEBS Lett 1998;
436:174-8. [PMID:
9781673 DOI:
10.1016/s0014-5793(98)01119-3]
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Abstract
Five 26-peptide analogues of the trypsin inhibitor [Pro18]CMTI-III containing Leu or Tyr in position 7 and Val or Tyr in position 27: 1 (Leu7, Tyr27), 2 (Tyr7, Val27), 3 (Tyr7, Tyr27), 4 (Leu7, Val27) and 5 (Leu7, Ala18, Tyr27) were synthesized by the solid-phase method. Analogues 1-4 displayed Ka with bovine beta-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 Tyr7 is involved in an additional aromatic interaction with position 41 of the enzyme.
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