Structure of the GcpE (IspG)-MEcPP complex from Thermus thermophilus.

Isoprenoid precursor biosynthesis occurs through the mevalonate or the methylerythritol phosphate (MEP) pathway, used i.e., by humans and by many human pathogens, respectively. In the MEP pathway, 2-C-methyl-D-erythritol-2,4-cyclo-diphosphate (MEcPP) is converted to (E)-1-hydroxy-2-methyl-but-2-enyl-4-diphosphate (HMBPP) by the iron-sulfur cluster enzyme HMBPP synthase (GcpE). The presented X-ray structure of the GcpE-MEcPP complex from Thermus thermophilus at 1.55Å resolution provides valuable information about the catalytic mechanism and for rational inhibitor design. MEcPP binding inside the TIM-barrel funnel induces a 60° rotation of the [4Fe-4S] cluster containing domain onto the TIM-barrel entrance. The apical iron of the [4Fe-4S] cluster ligates with the C3 oxygen atom of MEcPP.