EPR, ELECTRON-SPIN ECHO ENVELOPE MODULATION, AND ELECTRON-NUCLEAR DOUBLE-RESONANCE STUDIES OF THE 2FE2S CENTERS OF THE 2-HALOBENZOATE 1,2-DIOXYGENASE FROM BURKHOLDERIA (PSEUDOMONAS) CEPACIA 2CBS

The 2-halobenzoate 1,2-dioxygenase from Burkholderia (Pseudomonas) cep acia 2CBS (Fetzner, S., Muller, R., and Lingens, F. (1992) J. Bacterio l. 174, 279-290) contains both a ferredoxin-type and a Rieske-type 2Fe 2S center, These two significantly different 2Fe2S clusters were chara cterized with respect to their EPR spectra, electrochemical properties (Rieske-type cluster with g(z) = 2.025, g(y) = 1.91, g(x) = 1.79, g(a v) = 1.91, E(m) = -125 +/- 10 mV; ferredoxin-type center with g(z) = 2 .05, g(y) = 1.96, g(x) = 1.89, g(av) = 1.97, E(m) = -200 +/- 10 mV) an d pH dependence thereof, X band electron spin echo envelope modulation and electron nuclear double resonance spectroscopy was applied to stu dy the interaction of the Rieske-type center of the 2-halobenzoate 1,2 -dioxygenase with N-14 and H-1 nuclei in the vicinity of the 2Fe2S clu ster. The results are compared to those obtained on the Rieske protein of the cytochrome b(6)f complex (E(m) = +320 mV) and the water-solubl e ferredoxin (E(m) = -430 mV) of spinach chloroplasts, as typical repr esentatives of the g(av) = 1.91 and g(av) = 1.96 class of 2Fe2S center s, Properties common to all Rieske-type clusters and those restricted to the respective centers in bacterial oxygenases are discussed.