Expression, detection of candidate function and homology modeling for Vicia villosa ornithine δ-aminotransferase

Abstract

The accumulation of compatible solutes during stress in plant cell is well documented. Proline is one of these solutes which accumulate in the cytosol in response to drought or salinity stress in plants. Proline has several functions during stress just like osmotic adjustment, osmoprotection, free radical scavenger and antioxidant. Ornithine δ-aminotransferase (δ-OAT) is an important enzyme in proline biosynthetic pathway. It catalyzes the transamination of ornithine to pyrroline-5-carboxylate which can be reduced into proline. Expression of ornithine δ-aminotransferase gene isolated from Vicia villosa (VvOAT) showed protein with a molecular mass of 63 KDa which is compatible with the predicted mass and after VvOAT gene delivery into E. coli host HB101, VvOAT gene enhanced its salt tolerance. Homology modeling of VvOAT was performed based on the crystal structure of the ornithine δ-aminotransferase from humans (PDB code 2OATA). With this model, a flexible docking study with the substrate and inhibitors was performed. The results indicated that PHE170 and ASN171 in VvOAT are the important determinant residues in binding as they have strong hydrogen bonding contacts with the substrate and inhibitors. All the obtained results indicated the efficiency of utilizing this gene in conferring salt tolerance.