The invention provides a protein in a form that is functional for the enzymatic conversion of 2C-methyl-D-erythritol 2,4-cyclodiphosphate to 1-hydroxy-2-methyl-2-butenyl 4-diphosphate notably in its (E)-form of the non-mevalonate biosynthetic pathway to isoprenoids. The invention also provides a protein in a form that is functional for the enzymatic conversion of 1-hydroxy-2-methyl-2-butenyl 4-diphosphate, notably in its (E)-form, to isopentenyl diphosphate and/or dimethylallyl diphosphate. Further, screening methods for inhibitors of these proteins are provided. Further, 1-hydroxy-2-methyl-2-butenyl 4-diphosphate is provided and chemical and enzymatic methods of its preparation.