Compounds derived from mevalonic acid are required for growth of plant and animal cells. In plants, the mevalonic acid pathway participates in the synthesis of cytokinins, abscisic acid, gibberellins, ubiquinones, plastoquinones, dolichols, sterols, carotenoids, chlorophylls, and numerous other isoprenoids. However, it is not clear whether these small isoprenoids fully account for the mevalonic acid growth requirement of plant cells. In mammalian and yeast cells, it has been shown that products of mevalonic acid are covalently bound to G-proteins, low molecular weight ras-like GTP-binding proteins and nuclear lamins. Covalent attachment of isoprenoids to these proteins is required for their assembly into membranes and, hence, for their role in signal transduction and cell growth control. Given the recent discovery of G-proteins and ras-like GTP-binding proteins in plants, it was predicted that plants also contain isoprenylated proteins. Preliminary data shown in this proposal indicate that plants contain isoprenylated, membrane-associated proteins similar in mass to ras-like GTP-binding proteins and nuclear lamins. The goals of this project are to determine the structure of the isoprenoid modification of these proteins and to identify the proteins. This work will lead to and understanding of the role of protein isoprenylation in plant cell growth, phytohormone action, signal transduction, and membrane biogenesis. %%% Isoprenoids belong to a specialized class of lipid molecules. In animal cells, many proteins have been shown to be linked to isoprenoids. These proteins participate in cell division and other cellular processes. Current evidence suggests that the isoprenoid modification is essential for the biological activity of these proteins. This proposal presents the first evidence that plant cells also contain isoprenylated proteins. The goals of this project are to determine the chemical nature of the isoprenoids that are linked to plant proteins and to identify the respective proteins. This work will lead to an understanding of how the isoprenoid modification of proteins affects plant growth and development.
