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4Fe-4S-center
the enzyme contains [4F-4S] clusters
Ferredoxin
alternative electron donor besides flavodoxin is a two [4Fe-4S]1+/2+-cluster-containing ferredoxin, with redox potentials of 405 mV and 340mV. The flavodoxin is the dominant electron donor protein under iron-limiting conditions. The concentration of ferredoxin increases stepwise from about 0.2 micromol/g at 713 microM Fe to 1.1 micromol/g at 1745 microM Fe
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flavodoxin
dominant electron donor protein under iron-limiting conditions
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riboflavin
presence of trace amounts
riboflavin 5'-phosphate
1 mol per mol of heterodimeric dehydratase
riboflavin 5'-phosphate
the actual dehydration is mediated by component D, which contains 1.0 [4Fe-4S]2+ cluster, 1.0 reduced riboflavin-5'-phosphate and about 0.1 molybdenum (VI) per heterodimer
[4Fe-4S]-center
each active component contains an oxygen sensitive diamagnetic [4Fe-4S]2+ cluster. Reduction of the [4Fe-4S]2+ cluster of the activator protein with dithionite yields a paramagnetic [4Fe-4S]1+ cluster with the unusual electron spin ground state S=3/2. Under air the activator protein looses its activity within seconds due to irreversible degradation of its [4Fe-4S]2+ cluster to a [2Fe-2S]2+ cluster. The [4Fe-4S]2+ cluster of the heterodimeric dehydratase cannot be reduced to a [4Fe-4S]1+ cluster
[4Fe-4S]-center
the actual dehydration is mediated by component D, which contains 1.0 [4Fe-4S]2+ cluster, 1.0 reduced riboflavin-5'-phosphate and about 0.1 molybdenum (VI) per heterodimer
[4Fe-4S]-center
the reduced [4Fe-4S]+ cluster containing activator protein transfers one electron to the dehydratase driven by ATP hydrolysis, which activates the enzyme. With a tenfold excess of titanium(III) citrate at pH 8.0 the activator can be further reduced, yielding about 50% of a superreduced [4Fe-4S]0 cluster in the all-ferrous state. The superreduced cluster has apparent spectroscopic similarities with the corresponding [4Fe-4S]0 cluster described for the nitrogenase Fe-protein. Only one-electron transfer steps are involved in dehydratase catalysis
[4Fe-4S]-center
the [4Fe-4S](1+/2+) cluster of the activator protein is exposed to the solvent. Upon exchange of the bound ADP by ATP, the chelation rate by iron chelators is 8fold enhanced, indicating a large conformational change. Oxidized activator exhibits ATPase activity of 6 s(-1), which is completely abolished upon reduction by one electron
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Activator protein
the enzyme must be activated by an activator protein. Once activated, it can catalyse many turnovers
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activator protein HgdC
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the enzyme is activated by ATP, MgCl2, and Ti(III)citrate by an activator protein (HgdC) that is present in the organism at very low concentrations. It is suggested that during the activation step, the electron of this cycle is fed into the enzyme by Ti(III)citrate and energized by hydrolysis of ATP. Both functions are apparently catalysed by the activator. The enzyme remains in this activated state for several turnovers
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additional information
enzyme requires an activator protein HgdC for activity. Dehydratase activity is stimulated at least tenfold by cell-free extracts of Escherichia coli cells transformed with a plasmid carrying hgdC. On the chromosome the HgdC gene is located just before the catalytic subunits hgdA and hgdB
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additional information
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enzyme requires an activator protein HgdC for activity. Dehydratase activity is stimulated at least tenfold by cell-free extracts of Escherichia coli cells transformed with a plasmid carrying hgdC. On the chromosome the HgdC gene is located just before the catalytic subunits hgdA and hgdB
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Buckel, W.
The reversible dehydration of (R)-2-hydroxyglutarate to (E)-glutaconate
Eur. J. Biochem.
106
439-447
1980
Acidaminococcus fermentans, Acidaminococcus fermentans (P11569 and P11570), Acidaminococcus fermentans DSM 20731 (P11569 and P11570), [Clostridium] symbiosum
brenda
Schweiger, G.; Dutscho R.; Buckel, W.
Purification of 2-hydroxyglutaryl-CoA dehydratase from Acidaminococcus fermentans. An iron-sulfur protein
Eur. J. Biochem.
169
441-448
1987
Acidaminococcus fermentans (P11569 and P11570), Acidaminococcus fermentans, Acidaminococcus fermentans DSM 20731 (P11569 and P11570)
brenda
Hans, M.; Buckel, W.; Bill, E.
The iron-sulfur clusters in 2-hydroxyglutaryl-CoA dehydratase from Acidaminococcus fermentans. Biochemical and spectroscopic investigations
Eur. J. Biochem.
267
7082-7093
2000
Acidaminococcus fermentans (P11569 and P11570 and P11568), Acidaminococcus fermentans DSM 20731 (P11569 and P11570 and P11568)
brenda
Thamer, W.; Cirpus, I.; Hans, M.; Pierik, A.J.; Selmer, T.; Bill, E.; Linder, D.; Buckel, W.
A two [4Fe-4S]-cluster-containing ferredoxin as an alternative electron donor for 2-hydroxyglutaryl-CoA dehydratase from Acidaminococcus fermentans
Arch. Microbiol.
179
197-204
2003
Acidaminococcus fermentans (P11569 and P11570), Acidaminococcus fermentans DSM 20731 (P11569 and P11570)
brenda
Hans, M.; Bill, E.; Cirpus, I.; Pierik, A.J.; Hetzel, M.; Alber, D.; Buckel, W.
Adenosine triphosphate-induced electron transfer in 2-hydroxyglutaryl-CoA dehydratase from Acidaminococcus fermentans
Biochemistry
41
5873-5882
2002
Acidaminococcus fermentans (P11569 and P11570), Acidaminococcus fermentans DSM 20731 (P11569 and P11570)
brenda
Muller, U.; Buckel, W.
Activation of (R)-2-hydroxyglutaryl-CoA dehydratase from Acidaminococcus fermentans
Eur. J. Biochem.
230
698-704
1995
Acidaminococcus fermentans, Acidaminococcus fermentans ATCC 25085
brenda
Bendrat, K.; Mueller, U.; Klees, A.G.; Buckel, W.
Identification of the gene encoding the activator of (R)-2-hydroxyglutaryl-CoA dehydratase from Acidaminococcus fermentans by gene expression in Escherichia coli
FEBS Lett.
329
329-331
1993
Acidaminococcus fermentans (P11569 and P11570 and P11568), Acidaminococcus fermentans, Acidaminococcus fermentans DSM 20731 (P11569 and P11570 and P11568)
brenda
Hans, M.; Buckel, W.; Bill, E.
Spectroscopic evidence for an all-ferrous [4Fe-4S]0 cluster in the superreduced activator of 2-hydroxyglutaryl-CoA dehydratase from Acidaminococcus fermentans
J. Biol. Inorg. Chem.
13
563-574
2008
Acidaminococcus fermentans (P11569 and P11570 and P11568), Acidaminococcus fermentans DSM 20731 (P11569 and P11570 and P11568)
brenda
Locher, K.P.; Hans, M.; Yeh, A.P.; Schmid, B.; Buckel, W.; Rees, D.C.
Crystal structure of the Acidaminococcus fermentans 2-hydroxyglutaryl-CoA dehydratase component A
J. Mol. Biol.
307
297-308
2001
Acidaminococcus fermentans
brenda