Arabidopsis thaliana contains two differentially expressed 3-hydroxy-3-methylglutaryl-CoA reductase genes, wich encode microsomal forms of the enzyme
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...
| Autores: | , , , , , |
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| Formato: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 1994 |
| País: | España |
| Recursos: | Universidad de Barcelona |
| Repositorio: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/225620 |
| Acesso em linha: | https://hdl.handle.net/2445/225620 |
| Access Level: | acceso abierto |
| Palavra-chave: | Arabidopsis thaliana Biologia molecular vegetal Enzims Plant molecular biology Enzymes |
| Resumo: | 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. |
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