Modifications outside the proteinase binding loop in Cucurbita maxima trypsin inhibitor III (CMTI-III) analogues change the binding energy with bovine beta-trypsin.
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.
Faculty of Chemistry, University of Gdańsk, Poland.
A
A
Jaśkiewicz
K
K
Lis
J
J
Rózycki
G
G
Kupryszewski
K
K
Rolka
U
U
Ragnarsson
T
T
Zbyryt
T
T
Wilusz
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D020134:Catalytic Domain; D002417:Cattle; D004220:Disulfides; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry*; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D013816:Thermodynamics; D014357:Trypsin / Q000737:chemistry* / Q000378:metabolism; D014361:Trypsin Inhibitors / Q000737:chemistry* / Q000378:metabolism
C081870:CMTI protein, Cucurbita maxima; D004220:Disulfides; D010446:Peptide Fragments; D010455:Peptides; D010940:Plant Proteins; D014361:Trypsin Inhibitors; D014357:Trypsin