Wolinella succinogenes fumarate reductase contains a dihaem cytochrome b |
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Authors: | C Körtner F Lauterbach D Tripier G Unden A Kröger |
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Institution: | Institut für Mikrobiologie, J. W. Goethe-Universität, Theodor-Stern-Kai 7, Haus 75A, D-6000 Frankfurt, FRG.;Hoechst AG, Postfach 80 03 20. D-6230 Frankfurt 80, FRG. |
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Abstract: | The fumarate reductase operon of Wolinella succinogenes is made up of three structural genes (frd-CAB). The frdC gene was located next to the promoter region and identified as the cytochrome b structural gene encoding 256 amino acid residues. The N-terminal amino acid sequences of seven fragments derived from the cytochrome b moiety of the enzyme all mapped within the frdC gene. This suggested that the enzyme contained only one species of cytochrome b. Re-evaluation of earlier measurements of subunit composition, haem B content and molecular weight led to the conclusion that the enzyme contained one molecule of cytochrome b with two haem B groups. The hydropathy plot of the amino acid sequence predicted five membrane-spanning hydrophobic segments, the first four of which contained a single histidine residue each. These residues could form the axial ligands to the two haem B groups. FrdC was found to be homologous with the cytochrome b (SdhC) of the Bacillus subtilis succinate dehydrogenase, but not with the hydrophobic subunits of the fumarate reductase or succinate dehydrogenase of Escherichia coli. |
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