Dimethylsulfide (DMS) dehydrogenase is a complex heterotrimeric enzyme that catalyzes the oxidation of DMS to DMSO and allows Rhodovulum sulfidophilum to grow under photolithotrophic conditions with DMS as the electron donor. The enzyme is a 164 kDa heterotrimer composed of an a-subunit that binds a bis(molybdopterin guanine dinucleotide)Mo cofactor, a polyferredoxin ߭subunit, and a ?-subunit that contains a b-type heme. In this study, we describe the thermodynamic characterization of the redox centers within DMS dehydrogenase using EPR- and UV-visible-monitored potentiometry. Our results are compared with those of other bacterial Mo enzymes such as NarGHI nitrate reductase, selenate reductase, and ethylbenzene dehydrogenase. A remarkable similarity in the redox potentials of all Fe-S clusters is apparent.