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

• DOI: 10.1073/pnas.91.3.927
• Publication Date: 2006-05-31T13:03:01Z
• Authors: M Enjuto; L Balcells; N Campos; C Caelles; M Arró; A Boronat
• Keywords: Coding region

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 genes analyzed their structure expression. HMG2 consist of four exons three small introns interrupt coding sequence at equivalent positions. share similarity regions but not 5'- or 3'-flanking regions. mRNA is detected all tissues, whereas presence restricted to young seedlings, roots, inflorescences. between encoded proteins (HMGR1 HMGR2) corresponding membrane catalytic domains. HMGR2 represents a divergent form has no counterpart among HMGRs characterized so far. By using coupled vitro transcription-translation assay, we show both HMGR1 are cotranslationally inserted into endoplasmic reticulum-derived microsomal membranes. Our results suggest reticulum only cell compartment for targeting HMGR support hypothesis higher plants formation mevalonate occurs solely cytosol.