Spectroscopic investigations on the water-soluble fragment of the Rieske [2Fe 2S] protein from Paracoccus denitrificans

Abstract

A large-scale purification procedure has been developed to isolate the membrane-bound bc(1) complex of Paracoccus denitrificans. From the purified complex, a water-soluble fragment has been isolated. The fragment comprising residues 50-190 contains the Rieske [2Fe-2S] cluster and has an optical spectrum which is typical of such a cluster. The EPR spectrum of the cluster in the bc(1) complex differs slightly from the spectrum of the water-soluble fragment. Differences in the g values and linewidths of the resonances can be attributed to the absence of bound quinone in the water-soluble fragment. Signals from the cysteines and histidines that coordinate to the [2Fe-2S] cluster could be identified in the H-1 NMR spectrum of the fragment in solution. (C) 1998 Elsevier Science S.A. All rights reserved.