Abstract

A full-length cDNA encoding 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR, EC:1.1.1.34) was isolated from Clematis armandii by rapid amplification of cDNA ends (RACE), which was designated as CaHMGR. The full-length cDNA of CaHMGR (GenBank Accession No. JN830626) was 1874 bp containing a 1734 bp open reading frame (ORF) encoding a protein of 578 amino acids that contained four conserved domains and five transmembrane domain. Bioinformatic analysis revealed that the deduced amino acid sequence shared significant homology with other known plant HMGRs. The deduced protein had a calculated molecular weight of about 62.13 kDa and an isoelectric point (pI) of 8.47. The predicted 3-D structure showed that CaHMGR showed a similar spatial structure with other plant HMGRs. Phylogenetic tree analysis indicated that CaHMGR belonged to plant HMGR group. Tissue expression patterns revealed that CaHMGR expressed strongly in stems, and weakly in roots and leaves. Functional complementation of CaHMGR in a HMGR-deficient mutant yeast indicated that the cloned cDNA encoded a HMGR. CaHMGR is a novel and important enzyme involved in the biosynthesis of triterpenoid saponins in C. armandii.

Key words: 3-Hydroxy-3-methylglutaryl-CoA reductase (HMGR), Clematis armandiiFranch, cloning, expression profiles, functional identification.