EPR and Mossbauer studies of Benzoyl-CoA reductase

Benzoyl-CoA reductase catalyzes the two-electron transfer from a reduced fe rredoxin to the aromatic ring of benzoyl-CoA; this reaction is coupled to s toichiometrical ATP hydrolysis, A very low reduction potential (less than - 1V) is required for the first electron transfer to the aromatic ring, In th is work the nature of the redox centers of purified benzoyl-CoA reductase f rom Thauera aromatica was studied by EPR and Mossbauer spectroscopy. The re sults obtained indicated the presence of three [4Fe-4S] clusters. Redox tit ration studies revealed that the reduction potentials of all three clusters were below -500 mV. The previously reported S = 7/2 state of the enzyme du ring benzoyl-CoA-independent ATPase activity (Boll, M., Albracht, S. J, P., and Fuchs, G, (1997) fur. J. Biochem. 244, 840-851) was confirmed by Mossb auer spectroscopy. Inactivation by oxygen was associated with the irreversi ble conversion of part of the [4Fe-4S] clusters to [3Fe-4S] clusters. Acety lene stimulated the benzoyl-CoA-independent ATPase activity and induced nov el EPR signals with g(av) > 2. The presence of simple cubane clusters in be nzoyl-CoA reductase as the sole redox-active metal centers demonstrates nov el aspects of [4Fe-4S] clusters since they adopt the role of elemental sodi um or lithium which are used as electron donors in the analogous chemical B irch reduction of aromatic rings.