Publications

• Interactions between the molybdenum cofactor and iron-sulfur clusters of Escherichia coli dimethylsulfoxide reductase.

  Rothery R.A., Trieber C.A., Weiner J.H.

  We have used site-directed mutagenesis to study the interactions between the molybdo-bis(molybdopterin guanine dinucleotide) cofactor (Mo-bisMGD) and the other prosthetic groups of Escherichia coli Me2SO reductase (DmsABC). In redox-poised preparations, there is a significant spin-spin interaction ... >> More

  We have used site-directed mutagenesis to study the interactions between the molybdo-bis(molybdopterin guanine dinucleotide) cofactor (Mo-bisMGD) and the other prosthetic groups of Escherichia coli Me2SO reductase (DmsABC). In redox-poised preparations, there is a significant spin-spin interaction between the reduced Em,7 = -120 mV [4Fe-4S] cluster of DmsB and the Mo(V) of the Mo-bisMGD of DmsA. This interaction is significantly modified in a DmsA-C38S mutant that contains a [3Fe-4S] cluster in DmsA, suggesting that the [3Fe-4S] cluster is in close juxtaposition to the vector connecting the Mo(V) and the Em,7 = -120 mV cluster of DmsB. In a DmsA-R77S mutant, the interaction is eliminated, indicating the importance of this residue in defining the interaction pathway. In ferricyanide-oxidized glycerol-inhibited DmsAC38SBC, there is no detectable interaction between the oxidized [3Fe-4S] cluster and the Mo-bisMGD, except for a minor broadening of the Mo(V) spectrum. In a double mutant, DmsAS176ABC102SC, which contains an engineered [3Fe-4S] cluster in DmsB, no significant paramagnetic interaction is detected between the oxidized [3Fe-4S] cluster and the Mo(V). These results have important implications for (i) understanding the magnetic interactions between the Mo(V) and other paramagnetic centers and (ii) delineating the electron transfer pathway from the [4Fe-4S] clusters of DmsB to the Mo-bisMGD of DmsA. << Less

  J. Biol. Chem. 274:13002-13009(1999) [PubMed] [EuropePMC]

• Kinetic analysis and substrate specificity of Escherichia coli dimethyl sulfoxide reductase.

  Simala-Grant J.L., Weiner J.H.

  We have characterized the substrate specificity of dimethyl sulfoxide reductase (DmsABC) of Escherichia coli by determining Km and Kcat values for 22 different substrates. The enzyme has a very broad substrate specificity. The Km values varied 470-fold, while Kcat values varied only 20-fold, impli ... >> More

  We have characterized the substrate specificity of dimethyl sulfoxide reductase (DmsABC) of Escherichia coli by determining Km and Kcat values for 22 different substrates. The enzyme has a very broad substrate specificity. The Km values varied 470-fold, while Kcat values varied only 20-fold, implicating Km as the major determinant of Kcat/Km values. Sulfoxides and pyridine N-oxide exhibited the lowest Km values, followed by aliphatic N-oxides. The Kcat values for these compounds also followed the same pattern. Substitution at the 2 or 3 position of the pyridine N-oxide ring had little effect on Km while substitution at the 4 position had a greater effect, and increased Km. Negatively charged substrates were poorly accepted. A few compounds that are not S- or N-oxides were also reduced by the enzyme. Most compounds reduced by DmsABC were not toxic to E. coli under anaerobic growth conditions, and E. coli was able to use many of these compounds anaerobically as terminal electron acceptors in the presence of glycerol. Anaerobic growth on sulfoxides is solely due to DmsABC expression. However, there appears to be another as yet unidentified terminal reductase capable of using pyridine N-oxides as terminal electron acceptors. << Less

  Microbiology 142:3231-3239(1996) [PubMed] [EuropePMC]