Determinação das estruturas terciária e quaternária de uma lectina de sementes de Canavalia gladiata (Jacq.)DC na sua forma nativa e complexada com alfa-metil-manosídeo

Abstract

Lectins are proteins that have the ability to binding not covalently to carbohydrates and/or glycoproteins in a specific way. Lectins from Leguminous have been studied not only concerning to their physic/chemistry and biologics proprieties but in their three-dimensional molecules structures too. Canavalia gladiara seeds lectin (CGL) has been purified and crystallized using Sparse Matrix Method to research crystallization conditions in order to establish its three-dimensional structure. Protein crystals grown into 4 days at 20 ° C using vapour diffusion in sitting drops. Crystals were used to obtain the CGL complexed with alpha-methyl-mannoside by soaking. Using Synchrotron Light as source of X-rays, were obtained a diffraction data set at 1.99 A resolution to CGL and 2.22 A resolution to CGL complexed with alpha-methyl-mannoside. CGL structure was established with Canavalia ensiformis lectin as research model and showed a correlation coefficient of 93.0 °/0 with Rfactor 19.83 % and Rfree 23.87 %. At its final model 85.9 % residues are in widely allowed regions in Ramanchandran and 14.1 % in additional allowed regions. CGL with alpha-methylmannoside structure were molecular replacement determined with CGL structure as research model. The final structure showed Rfaccor 18.59 °/o and Rfree 24.57 % and correlation coefficient 93.9 %.