Squash trypsin inhibitor

Squash trypsin inhibitor EETI-II Epilancin 15x, novel antibiotic... 

P20D/V21K]-kalata B1 [W19K, P20N, V21K]-kalata B1 M81 mutant of squash trypsin inhibitor cmti-i... 

Nilges et al. used a very complete analytical treatment, but showed that the calculations would be tractable if a cutoff of 4 A were used, apparently without introducing too great an approximation.67 Applying the method to squash trypsin inhibitor, they found that atomic shifts of only 1 A greatly improved agreement with experimental data and that the previous isolated spin pair approximation had caused a slight systematic contraction of the structures. 

M. Nilges, J. Habazettl, A. T. Briinger, and T. A. Holak, J. Mol. Biol., 219, 499 (1991). Relaxation Matrix Refinement of the Solution Structure of Squash Trypsin Inhibitor. 

Heitz A, Hernandez JF, Gagnon J, Hong TT, Pham TT, Nguyen TM, Le-Nguyen D, Chiche L (2001) Solution structure of the squash trypsin inhibitor MCoTI-II. A new family for cyclic knottins. Biochemistry 40 7973-7983... 

Hernandez JF, Gagnon J, Chiche L, Nguyen TM, Andrieu JP, Heitz A, Trinh Hong T, Pham TT, Le Nguyen D (2000) Squash trypsin inhibitors from Momordica cochinchinensis exhibit an atypical macrocyclic structure. Biochemistry 39 5722-5730... 

The peptides discussed so far are defined by a common genetic pattern or architectural feature, such as their sequence or disulfide bond pattern. In this section we discuss peptides that share a common mode of action but may arise from different peptide families. Proteinase inhibitors (Pis) come in an astounding range of sizes, from the smallest gene-encoded cyclic peptide known to date, sunflower trypsin inhibitor 1 (SFTI-1), ° a 14-residue cyclic peptide with a single disulfide bond, to squash inhibitors that are approximately 30 residues in size and feature the cystine knot motif, to 53-residue Pis found in Nicotiana... 

Trypsin inhibitors in cucumber were first found in a study by Walker-Simmons et /. " after wounding of leaves and treatment with proteinase inhibitor-inducing factor (PIIF). The amino acid sequence of two inhibitors isolated from Cucurhita maxima (winter squash) were determined by Wilusz et at The peptides named ITD I and ITD 111 each comprised a 29-residue sequence with six cysteine residues. The only difference between the two peptides is in position 9, which is lysine in ITD I and glutamic acid in ITD III. The reactive site is located at the peptide bond between Arg5 and Ile6. Owing to their discovery and distribution in Cucurbitaceae the inhibitor family has been named squash inhibitors. Since the initial discoveries many other members of the squash family have been found. 

The seeds of squash plants are rich in a family of trypsin and chymotrypsin inhibitors that are approximately 35 amino acids in size and have been extensively investigated not only for their enzyme inhibitory activity, but also because they are very stable mini-protein scaffolds with applications in protein engineering. The best studied examples are Ecballium elaterium trypsin inhibitor (EETI-II) and Cucurbita maxima trypsin inhibitor (CMTI). Both X-ray and NMR have been used to characterise their structures, which incorporate a cystine-knot motif formed by three conserved disulphide bonds.93 We will describe this motif in more detail in a later section describing the plant cyclotides. 

Cucurbita maxima (squash) (Cucurbitaceae) [seed] Pumpkin fruit trypsin inhibitor (PFTI) (8 kDa 0 Cys) Trypsin [440, 442]... 

Two protein complexes were examined a complex consisting of bovine trypsin and CMTl-1 squash inhibitor (PDB ID of the complex IPPE [60]), and RNase SA in complex with barstar (PDB ID of the complex 1AY7 [61]). They consist of 252 and 185 residues, respectively. We prepare a set of decoy strucmres as described in the following, and select the right structure through free-energy calculations with the energy-representation method. 

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