Caracterização parcial de uma pro-lectina funcional de sementes de Dioclea grandiflora Benth expressa em Escherichia coli.

Abstract

The pro-lectin from Dioclea grandiflora presented active when expressed in recombinant (r-pro-DGL) in the cytoplasm of the model prokaryotic Escherichia coli. Obtained in soluble form from the pET32a vector, the recombinant protein presented apparent mass (25 kDa) and sequence (obtained by mass spectrometry) identical to the natural precursor, being unusually functional compared with other lectins of the pulses expressed heterologously having a specific activity of 134 217 728 (HU / mg). Unlike its counterpart wild r-Pro-DGL not specifically recognize glucose, and only weakly inhibited by mannose. Due to the high sequence homology among the forerunners in the subtribe lectins Diocleinae and galactose-binding lectin belonging to other tribes of legumes, there is the hypothesis that post-translational processing of this peculiar subtribe could influence decisively on the fine specificity of these proteins. However, the pro-r-DGL showed no affinity for galactose or lactose, showing that the topology of the binding site and the conformation of the loops that structure, the main specificity determinants of the monosaccharides. Thus, it can be stated that in the subtribe lectins precursors Diocleinae presents deglicosilados active while being still able to form oligomers and to establish cross-links between cell membranes.