Caracterização funcional e estrutural comparativa in silico de uma proteína PR-5 do tipo taumatina de Poncirus trifoliata.

Abstract

The search for new antifungal agents has directed efforts to proteins of innate immunity of plants, known as pathogenesis-related proteins, particularly the PR-5 family. To indicate new genes encoding antifungal proteins, among thousands of gene sequences available in databases, is a specialty of bioinformatics of the great interest in the post-genomic era, which requires knowledge on protein structure and function. In this context, this paper describes the comparative functional and structural in silico characterization of a PR-5 thaumatin-like protein of Poncirus trifoliata, called PtTLP, by using a strategy that involved modeling techniques and molecular docking. The proposed structure for PtTLP showed a stable and representative model within the evaluated patterns, which can be considered a very close representation of the actual structure of the protein. The structure obtained by comparative modeling showed typical features of TLPs proteins, including the existence of three areas, eight disulfide bounds and interdomain cleft eletronegativamente charged, called active site of the protein. The constructed model was deposited into the PMDB database, and it is online available. PtTLP interacts with the molecules of β-1,3-glucan, 1.4 -β-glucan, 1.6 -β-glucan, N-acetylglucosamine, 1,3-β-D-glucose and 1,4-β- D-glucose, with interactions evidenced by negative energies and the orientation of the structures in the region comprising the active site of the protein, unlikely the interaction with the chitin molecule, which showed positive binding energy and anchored off the protein active site. These data provide evidence for possible β-glucanase activities and binding the monomers of soluble carbohydrates to PtTLP and open up a range of issues to be investigated on this protein. These activities need to be experimentally proven, since this protein is a strong candidate, as antifungal and antioomycetal, for biotechnological applications in agriculture, pharmaceutical and food industry.