Molecular cloning and structural characterization of HMG-CoA reductase gene from Catharanthus roseus (L.) G. Donn. cv. Albus

The 3-hydroxy-3-methyl glutaryl-CoA reductase (HMGR) catalyzes the conversion of HMG-CoA to mevalonate, the first committed step in isoprenoid biosynthesis pathway in plants. HMG-CoA reductase gene was amplified from the Catharanthus roseus (L.) G. Donn. cv. Albus by polymerase chain reaction (PCR) with primers designed using published sequence of HMG-CoA reductase c-DNA of C. roseus cv. Little Delicata (Acc. No. M96068). PS2 SERVER was used to generate three dimensional (3-D) structure of the enzyme using human HMG-CoA reductase as template. The structure was evaluated at various web interfaced servers, i.e., PROCHEK, Profunc and PDBsum, for checking the stereo interfaced quality of the structure in terms of bonds, bond angles, dihedral angles, structural as well as functional domains. The generated model was visualized using the Rasmol. The results of these studies revealed that HMG-CoA reductase gene from cv. Albus had 99% sequence homology with hmgr cDNA of cv. Little Delicata. The amino acid sequence of the HMGR protein of cv. Albus was found closely related to the members of the family Solanaceae and distantly related to the members of the families Euphorbiaceae and Brassicaceae. The enzyme has N-terminal transmembrane domain and a C-terminal catalytic domain with active sites that can bind to HMG-CoA and NADPH(2). The fold of the substrate domain is unique and resembles the prism with 28-residue helix forming the central core. The homology model of enzyme generated in the present study, hence, could be used in determining the mechanistic function of this important class of proteins.