GERANYLGERANYL PYROPHOSPHATE SYNTHASE ENCODED BY THE NEWLY ISOLATED GENE GGPS6 FROM ARABIDOPSIS-THALIANA IS LOCALIZED IN MITOCHONDRIA

We have cloned a new geranylgeranyl pyrophosphate (GGPP) synthase gene , designated GGPS6, from Arabidopsis thaliana genomic DNA. Nucleotide sequence analysis revealed that the GGPS6 gene contains an open readin g frame coding for a protein of 343 amino acid residues with a calcula ted molecular mass of 37 507 Da. Also, the gene is not interrupted by an intron. The predicted amino acid sequence of the GGPS6 gene shows s ignificant homology (34.0-57.7%) with other GGPP synthases from Arabid opsis. The GGPS6 protein contains a N-terminal signal peptide which is thought to function as an organelle targeting sequence. In fact, the GGPS6-GFP fusion protein was found to be localized exclusively in mito chondria when expressed in tobacco BY-2 cells. In vitro analysis of th e enzyme activity as well as genetic complementation analysis with Erw inia uredovora crt gene cluster expressed in Escherichia coli showed t hat the GGPS6 gene most certainly encodes a GGPP synthase catalyzing t he conversion of farnesyl pyrophosphate to GGPP.