RESUMO
We report the molecular characterization of ß-1,3-glucanase-producing Bacillus amyloliquefaciens-an endophyte of Hevea brasiliensis antagonistic to Phytophthora meadii. After cloning and sequencing, the ß-1,3-glucanase gene was found to be 747 bp in length. A homology model of the ß-1,3-glucanase protein was built from the amino acid sequence obtained upon translation of the gene. The target ß-1,3-glucanase protein and the template protein, endo ß-1,3-1,4-glucanase protein (PDB ID: 3o5s), were found to share 94% sequence identity and to have similar secondary and tertiary structures. In the modeled structure, three residues in the active site region of the template-Asn52, Ile157 and Val158-were substituted with Asp, Leu and Ala, respectively. Computer-aided docking studies of the substrate disaccharide (ß-1, 3-glucan) with the target as well as with the template proteins showed that the two protein-substrate complexes were stabilized by three hydrogen bonds and by many van der Waals interactions. Although the binding energies and the number of hydrogen bonds were the same in both complexes, the orientations of the substrate in the active sites of the two proteins were different. These variations might be due to the change in the three amino acids in the active site region of the two proteins. The difference in substrate orientation in the active site could also affect the catalytic potential of the ß-1,3 glucanase enzyme.
