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Coevolution of insect trypsins and inhibitors
A R Lopes1, M A Juliano, L Juliano
1Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, C.P. 26077, 05513-970, São Paulo, Brazil.
Archives of Insect Biochemistry and Physiology
|February 26, 2004
Summary
Insect trypsins have evolved to resist plant proteinase inhibitors (PIs). Lepidopteran trypsins show adaptations in their active sites, leading to decreased binding and increased hydrolysis of PIs.
Area of Science:
- Biochemistry
- Entomology
- Molecular Biology
Background:
- Plant proteinase inhibitors (PIs) often feature lysine at the P1 position.
- Insect trypsins, particularly in Lepidoptera, have evolved resistance mechanisms against PIs.
Purpose of the Study:
- To investigate the molecular basis of insect trypsin resistance to plant proteinase inhibitors.
- To identify specific amino acid residues in insect trypsins responsible for differential inhibitor interactions.
Main Methods:
- Sequence alignment of sensitive and insensitive insect trypsins with porcine trypsin.
- Analysis of conserved and variable residues around the active site.
- Neighbor Joining analysis to infer evolutionary relationships.
Main Results:
- Lepidopteran trypsins exhibit more hydrophobic substrate binding subsites compared to other insect orders.
- Specific residues (e.g., 60, 94, 97-99, 188, 190, 213-219, 228) were identified as crucial for insect trypsin-PI interactions.
- These residues are located near the active site, including the S1 and S4 pockets.
Conclusions:
- Insect trypsin resistance to PIs involves adaptations in active site residues.
- Hydrophobic subsites and specific amino acid substitutions contribute to reduced binding and increased hydrolysis of PIs in Lepidopteran insects.