EVOLUTIONAL AND FUNCTIONALANALYSIS OF A SERINE PROTEASEIN Spodoptera litura

摘要

Spodoptera litura is a threatening agricultural insect in tropical andsubtropical areas and accounts for tremendous annual crop losses. As seenin virtually all insect species, serine proteases (SPs) are crucial to S. litura.The expression pattern of SPs from the midgut of S. litura was studiedthrough expressed sequence tags (ESTs) analysis. One of SP (SlSP1) waschosen for detailed study, because the expression of the gene was midgutand larvae specific. SlSP1 was conducted as a model of its evolution,structure, and potential binding activity with corresponding substrates.SlSP1 is composed of 255 amino acids including a signal peptide atN-terminal followed by a putative activation peptide and the matureprotein along with five putative phosphorylation sites, three disulphidebridges, and two N-glycosylation positions. At least nine conserved motifs were obtained in multiple sequence alignments. Some conserved residues, such as the catalytic triad His84, Asp127, and Ser229 as well as sixcysteines at position 66, 82, 194, 211, 223, and 247, were examined.After homology modeling and molecular dynamics simulation, theresultant three-dimensional (3D) structure of SlSP1 was docked with thesubstrates 2PTC-Arg and 2PTC-Lys, respectively. MolecularMechanic/Poisson–Boltzmann surface area analysis was applied toanticipate optimal binding mode and crucial active sites of this enzyme.The residues Trp28, Gly187, Aso188, Arg249, Ile250, Lys246, andLys278 are crucial for the substrate binding and molecule process. Thisinformation can be used in logical design of SPs inhibitors. New inhibitorsmay be a basis for development of a new pest control technology.