Arabidopsis thaliana contains two differentially expressed 3-hydroxy-3-methylglutaryl-CoA reductase genes, which encode microsomal forms of the enzyme.

0301 basic medicine 0303 health sciences Base Sequence Sequence Homology, Amino Acid Arabidopsis Proteins Molecular Sequence Data Arabidopsis Chromosome Mapping Gene Expression DNA Intracellular Membranes Endoplasmic Reticulum Genes, Plant Isoenzymes 03 medical and health sciences Hydroxymethylglutaryl-CoA-Reductases, NADP-dependent Microsomes Hydroxymethylglutaryl CoA Reductases Amino Acid Sequence Cloning, Molecular
DOI: 10.1073/pnas.91.3.927 Publication Date: 2006-05-31T13:03:01Z
ABSTRACT
The enzyme 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR; EC 1.1.1.34) catalyzes the first rate-limiting step in plant isoprenoid biosynthesis. Arabidopsis thaliana contains two genes, HMG1 and HMG2, that encode HMGR. We have cloned these two genes and analyzed their structure and expression. HMG1 and HMG2 consist of four exons and three small introns that interrupt the coding sequence at equivalent positions. The two genes share sequence similarity in the coding regions but not in the 5'- or 3'-flanking regions. HMG1 mRNA is detected in all tissues, whereas the presence of HMG2 mRNA is restricted to young seedlings, roots, and inflorescences. The similarity between the two encoded proteins (HMGR1 and HMGR2) is restricted to the regions corresponding to the membrane and the catalytic domains. Arabidopsis HMGR2 represents a divergent form of the enzyme that has no counterpart among plant HMGRs characterized so far. By using a coupled in vitro transcription-translation assay, we show that both HMGR1 and HMGR2 are cotranslationally inserted into endoplasmic reticulum-derived microsomal membranes. Our results suggest that the endoplasmic reticulum is the only cell compartment for the targeting of HMGR in Arabidopsis and support the hypothesis that in higher plants the formation of mevalonate occurs solely in the cytosol.
SUPPLEMENTAL MATERIAL
Coming soon ....
REFERENCES (0)
CITATIONS (146)