EPR and Mössbauer studies of benzoyl-CoA reductase.
Benzoyl-CoA reductase catalyzes the two-electron transfer from a reduced ferredoxin to the aromatic ring of benzoyl-CoA; this reaction is coupled to stoichiometrical ATP hydrolysis. A very low reduction potential (less than -1 V) is required for the first electron transfer to the aromatic ring. In this work the nature of the redox centers of purified benzoyl-CoA reductase from Thauera aromatica was studied by EPR and Mössbauer spectroscopy. The results obtained indicated the presence of three [4Fe-4S] clusters. Redox titration studies revealed that the reduction potentials of all three clusters were below -500 mV. The previously reported S = 7/2 state of the enzyme during benzoyl-CoA-independent ATPase activity (Boll, M., Albracht, S. J. P., and Fuchs, G. (1997) Eur. J. Biochem. 244, 840-851) was confirmed by Mössbauer spectroscopy. Inactivation by oxygen was associated with the irreversible conversion of part of the [4Fe-4S] clusters to [3Fe-4S] clusters. Acetylene stimulated the benzoyl-CoA-independent ATPase activity and induced novel EPR signals with g(av) >2. The presence of simple cubane clusters in benzoyl-CoA reductase as the sole redox-active metal centers demonstrates novel aspects of [4Fe-4S] clusters since they adopt the role of elemental sodium or lithium which are used as electron donors in the analogous chemical Birch reduction of aromatic rings.
Boll
M
M
Biological Chemistry Department, John Innes Centre, Colney, Norwich NR4 7UH, United Kingdom. boll@uni-freiburg.de
Fuchs
G
G
Meier
C
C
Trautwein
A
A
Lowe
D J
DJ
D000114:Acetylene / Q000494:pharmacology; D000214:Acyl Coenzyme A / Q000378:metabolism / Q000494:pharmacology; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000266:Adenylyl Imidodiphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000345:Affinity Labels; D001386:Azides / Q000494:pharmacology; D001665:Binding Sites; D004227:Dithionite / Q000494:pharmacology; D004578:Electron Spin Resonance Spectroscopy; D004789:Enzyme Activation / Q000187:drug effects; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry*; D044925:Oxidoreductases Acting on CH-CH Group Donors; D010100:Oxygen / Q000378:metabolism / Q000494:pharmacology; D015204:Spectroscopy, Mossbauer; D013696:Temperature; D020628:Thauera / Q000201:enzymology*
D000214:Acyl Coenzyme A; D000345:Affinity Labels; D001386:Azides; D007506:Iron-Sulfur Proteins; D004227:Dithionite; D000266:Adenylyl Imidodiphosphate; C037817:benzoyl-coenzyme A; C036313:N-4-azido 2-nitrophenyl gamma-aminobutyryl-5-adenylyl imidodiphosphate; D000255:Adenosine Triphosphate; D010088:Oxidoreductases; D044925:Oxidoreductases Acting on CH-CH Group Donors; C109030:benzoyl-coenzyme A reductase (dearomatizing); D000251:Adenosine Triphosphatases; D000114:Acetylene; D010100:Oxygen