An iron-sulfur protein found in plant chloroplasts and cyanobacteria that contains a [4Fe-4S] cluster . Forms part of an alternative non-mevalonate pathway for isoprenoid biosynthesis. Bacteria have a similar enzyme that uses flavodoxin rather than ferredoxin (cf. EC 188.8.131.52). The enzyme from the plant Arabidopsis thaliana is active with photoreduced 5-deazaflavin but not with flavodoxin .
(E)-4-hydroxy-3-methylbut-2-enyl diphosphate synthase converts 2-C-methyl-D-erythritol-2,4-cyclodiphosphate into (E)-4-hydroxy-3-methyl-but-2-enyl diphosphate in the penultimate step of the methyl-erythritol phosphate pathway for isoprene biosynthesis, pathway overview