The Saccharomyces cerevisiae succinate dehydrogenase (SDH) of the mitochondrial electron transport chain oxidizes succinate and reduces ubiquinone. Using a random mutagenesis approach, we identified functionally important amino acid residues in one of the anchor subunits, Sdh4p. We analyzed three point mutations (F69V, S71A, and H99L) and one nonsense mutation (Y89OCH) that truncates the Sdh4p subunit at the third predicted transmembrane segment. The F69V and the S71A mutations result in greatly impaired respiratory growth in vivo and quinone reductase activities in vitro, with negligible effects on enzyme stability. In contrast, the Y89OCH and the H99L mutations elicit large structural perturbations that impair assembly as evidenced by reduced covalent FAD levels, membrane-associated succinate-phenazine methosulfate reductase activities, and thermal stability. We propose that the Phe-69 and the Ser-71 residues are involved in the formation of a quinone-binding site, whereas the His-99 residue is at the interface of the peripheral and the membrane domains. In addition, the properties of the Y89OCH mutation are consistent with the interpretation that the third transmembrane segment is not involved in catalysis but rather plays an important structural role. The mutant enzymes are differentially sensitive to a quinone analog inhibitor, providing further evidence for a two-quinone binding model in the yeast SDH.
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Evidence ID | Analyze ID | Gene/Complex | Systematic Name/Complex Accession | Qualifier | Gene Ontology Term ID | Gene Ontology Term | Aspect | Annotation Extension | Evidence | Method | Source | Assigned On | Reference |
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Evidence ID | Analyze ID | Gene | Gene Systematic Name | Phenotype | Experiment Type | Experiment Type Category | Mutant Information | Strain Background | Chemical | Details | Reference |
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Evidence ID | Analyze ID | Gene | Gene Systematic Name | Disease Ontology Term | Disease Ontology Term ID | Qualifier | Evidence | Method | Source | Assigned On | Reference |
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Evidence ID | Analyze ID | Regulator | Regulator Systematic Name | Target | Target Systematic Name | Direction | Regulation of | Happens During | Regulator Type | Direction | Regulation Of | Happens During | Method | Evidence | Strain Background | Reference |
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Site | Modification | Modifier | Source | Reference |
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Evidence ID | Analyze ID | Interactor | Interactor Systematic Name | Interactor | Interactor Systematic Name | Allele | Assay | Annotation | Action | Phenotype | SGA score | P-value | Source | Reference | Note |
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Evidence ID | Analyze ID | Interactor | Interactor Systematic Name | Interactor | Interactor Systematic Name | Assay | Annotation | Action | Modification | Source | Reference | Note |
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Complement ID | Locus ID | Gene | Species | Gene ID | Strain background | Direction | Details | Source | Reference |
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Evidence ID | Analyze ID | Dataset | Description | Keywords | Number of Conditions | Reference |
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