Studies on the nonmevalonate pathway to terpenes: The role of the GcpE (IspG) protein

Recombinant Escherichia coli cells engineered for the expression of the xyIB gene in conjunction with genes of the nonmevalonate pathway were supplied with C-13-labeled 1-deoxy-D-xylulose. Cell extracts were analyzed directly by NMR spectroscopy. C-13-labeled 2C-methyl-D-erythritol 2,4-cyclodiphosphate was detected at high levels in cells expressing xyIB, ispC, ispD, ispE, and ispF. The additional expression of the gcpE gene afforded 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate as an intermediate of the nonmevalonate pathway. Hypothetical mechanisms involving conserved cysteine residues are proposed for the enzymatic conversion of 2C-methyl-D-erythritol 2,4-cyclodiphosphate into 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate catalyzed by the GcpE protein.