Isoprenoid biosynthesis in chloroplasts via the methylerythritol phosphate pathway: the (E)-4-hydroxy-3-methylbut-2-enyl diphosphate synthase (GcpE) from Arabidopsis thaliana is a [4Fe-4S] protein.
The mevalonate-independent methylerythritol phosphate pathway is widespread in bacteria. It is also present in the chloroplasts of all phototrophic organisms. Whereas the first steps, are rather well known, GcpE and LytB, the enzymes catalyzing the last two steps have been much less investigated. 2-C-Methyl-D-erythritol 2,4-cyclodiphosphate is transformed by GcpE into 4-hydroxy-3-methylbut-2-enyl diphosphate, which is converted by LytB into isopentenyl diphosphate or dimethylallyl diphosphate. Only the bacterial GcpE and LytB enzymes have been investigated to some extent, but nothing is known about the corresponding plant enzymes. In this contribution, the prosthetic group of GcpE from the plant Arabidopsis thaliana and the bacterium Escherichia coli has been fully characterized by Mossbauer spectroscopy after reconstitution with (57)FeCl(3), Na(2)S and dithiothreitol. It corresponds to a [4Fe-4S] cluster, suggesting that both plant and bacterial enzymes catalyze the reduction of 2-C-methyl-D-erythritol 2,4-cyclodiphosphate into (E)-4-hydroxy-3-methylbut-2-enyl diphosphate via two consecutive one-electron transfers. In contrast to the bacterial enzyme, which utilizes NADPH/flavodoxin/flavodoxin reductase as a reducing shuttle system, the plant enzyme could not use this reduction system. Enzymatic activity was only detected in the presence of the 5-deazaflavin semiquinone radical.
Seemann
Myriam
M
Institut Le Bel, UMR 7123 CNRS, Université Louis Pasteur, Strasbourg, France.
Wegner
Patrick
P
Schünemann
Volker
V
Bui
Bernadette Tse Sum
BT
Wolff
Murielle
M
Marquet
Andrée
A
Trautwein
Alfred X
AX
Rohmer
Michel
M
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010088:Oxidoreductases; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013729:Terpenes / Q000737:chemistry / Q000378:metabolism*
D029681:Arabidopsis Proteins; D013729:Terpenes; D010088:Oxidoreductases; C000708271:AT5G60600 protein, Arabidopsis