Publications

• Sulfide oxidation in the phototrophic sulfur bacterium Chromatium vinosum.

  Reinartz M., Tschape J., Bruser T., Truper H.G., Dahl C.

  Sulfide oxidation in the phototrophic purple sulfur bacterium Chromatium vinosum D (DSMZ 180(T)) was studied by insertional inactivation of the fccAB genes, which encode flavocytochrome c, a protein that exhibits sulfide dehydrogenase activity in vitro. Flavocytochrome c is located in the periplas ... >> More

  Sulfide oxidation in the phototrophic purple sulfur bacterium Chromatium vinosum D (DSMZ 180(T)) was studied by insertional inactivation of the fccAB genes, which encode flavocytochrome c, a protein that exhibits sulfide dehydrogenase activity in vitro. Flavocytochrome c is located in the periplasmic space as shown by a PhoA fusion to the signal peptide of the hemoprotein subunit. The genotype of the flavocytochrome-c-deficient Chr. vinosum strain FD1 was verified by Southern hybridization and PCR, and the absence of flavocytochrome c in the mutant was proven at the protein level. The oxidation of thiosulfate and intracellular sulfur by the flavocytochrome-c-deficient mutant was comparable to that of the wild-type. Disruption of the fccAB genes did not have any significant effect on the sulfide-oxidizing ability of the cells, showing that flavocytochrome c is not essential for oxidation of sulfide to intracellular sulfur and indicating the presence of a distinct sulfide-oxidizing system. In accordance with these results, Chr. vinosum extracts catalyzed electron transfer from sulfide to externally added duroquinone, indicating the presence of the enzyme sulfide:quinone oxidoreductase (EC 1.8.5.-). Further investigations showed that the sulfide:quinone oxidoreductase activity was sensitive to heat and to quinone analogue inhibitors. The enzyme is strictly membrane-bound and is constitutively expressed. The presence of sulfide:quinone oxidoreductase points to a connection of sulfide oxidation to the membrane electron transport system at the level of the quinone pool in Chr. vinosum. << Less

  Arch Microbiol 170:59-68(1998) [PubMed] [EuropePMC]

• Purification and characterization of sulfide-quinone reductase, a novel enzyme driving anoxygenic photosynthesis in Oscillatoria limnetica.

  Arieli B., Shahak Y., Taglicht D., Hauska G., Padan E.

  An enzyme catalyzing sulfide quinone oxido-reduction (E.C.1.8.5.'.; SQR) has been purified in an active form, from thylakoids of the cyanobacterium Oscillatoria limnetica. It is composed of a single polypeptide of about 57 kDa. The catalytic activity of the purified enzyme is similar to the membra ... >> More

  An enzyme catalyzing sulfide quinone oxido-reduction (E.C.1.8.5.'.; SQR) has been purified in an active form, from thylakoids of the cyanobacterium Oscillatoria limnetica. It is composed of a single polypeptide of about 57 kDa. The catalytic activity of the purified enzyme is similar to the membrane-bound form in its kinetic parameters: apparent Km for sulfide equals 8 microM; Vmax of 100-150 mumol of plastoquinone-1 reduced/mg protein/h; quinone-substrate specificity; differential sensitivity to quinone analog inhibitors, the most potent of which being aurachin C (I50 = 7 nM), and specific inducibility by sulfide. Taken together, they suggest that the purified SQR is the enzyme catalyzing anoxygenic photosynthesis in cyanobacteria. The UV and visible absorption and fluorescence spectra of the purified SQR are typical of a flavoprotein. Both the absorption and fluorescence intensities are reduced by sulfide. The SQR activity is inhibited by KCN, a flavoprotein inhibitor. We have sequenced so far 29 amino acid residues of the SQR NH2 terminus and found that from the second residue, this sequence contains the highly conserved fingerprint of the NAD/FAD-binding domain of many NAD/FAD-binding enzymes (Wierenga, R. K., Terpstra, P., and Hol, W. G. S. (1986) J. Mol. Biol. 187, 101-107). This suggests that the SQR enzyme is a flavoprotein which contains binding sites for sulfide and quinone and that the electron transfer between the two is mediated by FAD. << Less

  J Biol Chem 269:5705-5711(1994) [PubMed] [EuropePMC]