title: Molecular insights into mechanisms of lepidopteran serine proteinase resistance to natural plant defenses.
abstract: Plants have a wide range of chemical defenses against predation, including substances that target digestive serine proteinases of herbivorous. Previous works demonstrated that lepidopteran insects have digestive serine proteinases resistant to plant proteinase inhibitors (PPIs) and ketone modifications, while coleopteran ones are sensitive to those plant defenses. This paper focuses on molecular aspects that lead lepidopteran serine proteinases to PPI and ketone modification resistance. Using biochemical experiments and computer 3D modeling we demonstrated that lepidopteran trypsins are more hydrophobic than coleopteran ones, a feature associated to trypsin oligomerization and decreased inhibition by PPI. Moreover, the determination of pKa values of chymotrypsin catalytic residues obtained by TPCK modification indicates that the environment around the active site of ketone-resistant and -sensitive chymotrypsins are different. Structural analysis using resistant and sensitive chymotrypsins data allowed us to point 2 hotspot regions around the active site that could explain the observed differences. Our set of results highlights features of serine proteinases important for understanding the resistance of insects to plant chemical defenses.
authors.affiliation: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, C.P. 26077, 05513-970 São Paulo, Brazil.
authors.forename: Fábio K
authors.initials: FK
authors.lastname: Tamaki
authors.affiliation: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, C.P. 26077, 05513-970 São Paulo, Brazil. Electronic address: warterra@iq.usp.br.
authors.forename: Walter R
authors.initials: WR
authors.lastname: Terra
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D007915:Lepidoptera / Q000201:enzymology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D018521:Plant Physiological Phenomena; D017386:Sequence Homology, Amino Acid; D057057:Serine Proteases / Q000737:chemistry / Q000378:metabolism*; D015842:Serine Proteinase Inhibitors / Q000378:metabolism
chemical_list: D015842:Serine Proteinase Inhibitors; D057057:Serine Proteases
keywords: Insect-plant interaction; Ketone modification; Plant-proteinase inhibitors; Resistant serine-Proteinase