Heterodisulfide Reductase from Methanol-Grown Cells of Methanosarcina Barkeri is not a Flavoenzyme
| العنوان: | Heterodisulfide Reductase from Methanol-Grown Cells of Methanosarcina Barkeri is not a Flavoenzyme |
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| المؤلفون: | Martin Vaupel, Reiner Hedderich, Rudolf K. Thauer, Andreas Künkel, Steffen Heim |
| المصدر: | European Journal of Biochemistry. 244:226-234 |
| بيانات النشر: | Wiley, 1997. |
| سنة النشر: | 1997 |
| مصطلحات موضوعية: | Iron-Sulfur Proteins, Transcription, Genetic, Protein subunit, Molecular Sequence Data, ved/biology.organism_classification_rank.species, Flavoprotein, Flavin group, Reductase, Biochemistry, Open Reading Frames, Flavins, Operon, Amino Acid Sequence, Ferredoxin, Base Sequence, Flavoproteins, biology, ved/biology, Methanol, Active site, Ferredoxin-thioredoxin reductase, Cytochrome b Group, Culture Media, Genes, Bacterial, biology.protein, Methanosarcina barkeri, Oxidoreductases |
| الوصف: | Heterodisulfide reductase from methanol-grown cells of Methanosarcina barkeri (MbHdrDE) is a membrane-bound enzyme composed of a 46-kDa subunit MbHdrD and a 23-kDa subunit MbHdrE. The enzyme has been shown to contain 0.6 mol heme and 20 mol Fe/S per mol heterodimer. In addition, substoichiometric amounts of FAD, thought to be an essential component of the active enzyme, were detected. We have now obtained preparations of active heterodisulfide reductase in high yields completely devoid of a flavin. Cloning and sequencing of the genes encoding MbHdrD and MbHdrE, which were found to form a transcription unit hdrED, revealed that both subunits also lack an FAD-binding motif. MbHdr thus differs from heterodisulifde reductase from Methanobacterium thermoautotrophicum (MtHdr), which is a flavo iron-sulfur protein composed of the subunits MtHdrA (80 kDa), MtHdrB (36 kDa) and MtHdrC (21 kDa), the subunit HdrA harboring the flavin-binding site. Sequence comparisons revealed that the N-terminal third of MbHdrD, which contained two sequence motifs for [4Fe-4S] clusters, is similar to MtHdrC and that the C-terminal two thirds of MbHdrD are similar to MtHdrB. Thus, MbHdrD and MtHdrC are structurally equivalent subunits. MbHdrE shows sequence similarity to b-type cytochromes, in agreement with the finding that this subunit contains a heme. These and other results indicate that MbHdrD harbors the active site of heterodisulfide reduction and that a flavin is not involved in catalysis. Since MbHdrD contains only iron-sulfur clusters, a mechanism of disulfide reduction involving one electron rather than two electron-transfer reactions has to be considered such as operative in ferredoxin :thioredoxin reductases from chloroplasts and cyanobacteria. |
| تدمد: | 1432-1033 0014-2956 |
| DOI: | 10.1111/j.1432-1033.1997.00226.x |
| URL الوصول: | https://explore.openaire.eu/search/publication?articleId=doi_dedup___::a633f348509b0908ad4da27376358339 https://doi.org/10.1111/j.1432-1033.1997.00226.x |
| Rights: | OPEN |
| رقم الانضمام: | edsair.doi.dedup.....a633f348509b0908ad4da27376358339 |
| قاعدة البيانات: | OpenAIRE |
| تدمد: | 14321033 00142956 |
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| DOI: | 10.1111/j.1432-1033.1997.00226.x |