Cytidine 5 '-triphosphate-dependent biosynthesis of isoprenoids: YgbP protein of Escherichia coli catalyzes the formation of 4-diphosphocytidyl-2-C-methylerythritol

2-C-methylerythritol 4-phosphate has been established recently as an interm ediate of the deoxyxylulose phosphate pathway used for biosynthesis of terp enoids in plants and in many microorganisms. We show that an enzyme isolate d from cell extract of Escherichia coli converts 2-C-methylerythritol 4-pho sphate into 4-diphosphocytidyl-2-C-methylerythritol by reaction with CTP. T he enzyme is specified by the hitherto unannotated ORF ygbP of E. coli. The cognate protein was obtained in pure form from a recombinant hyperexpressi on strain of E. coli harboring a plasmid with the ygbP gene under the contr ol of a T5 promoter and lac operator. By using the recombinant enzyme, 4-di phosphocytidyl-[2-C-14]2-C-methylerythritol was prepared from [2-C-14]2-C-m ethylerythritol 4-phosphate. The radiolabeled 4-diphosphocytidyl-2-C-methyl erythritol was shown to be efficiently incorporated into carotenoids by iso lated chromoplasts of Capsicum annuum. The E. coli ygbP gene appears to be part of a small operon also comprising the unannotated ygbB gene. Genes wit h similarity to ygbP and ygbB are present in the genomes of many microorgan isms, and their occurrence appears to be correlated with that of the deoxyx ylulose pathway of terpenoid biosynthesis. Moreover, several microorganisms have genes specifying putative fusion proteins with ygbP and ygbB domains, suggesting that both the YgbP protein and the YgbB protein are involved in the deoxyxylulose pathway. A gene from Arabidopsis thaliana with similarit y to ygbP carries a putative plastid import sequence, which is well in line with the assumed localization of the deoxyxylulose pathway in the plastid compartment of plants.