A role for plastids in plant protein isoprenylation.

Protein isoprenylation refers to the attachment of a C farnesyl or C geranylgeranyl moiety to a carboxyl terminal cysteine residue. Because protein isoprenyltransferases are cytosolic enzymes, it has long been assumed that the isoprenyl diphosphates used for protein isoprenylation are synthesized in the cytosol. However, in the present work, we established that the plastidial 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway is predominantly responsible for providing the geranylgeranyl diphosphate for protein geranylgeranylation in tobacco BY-2 cells.