Hydrophobic membrane anchor subunit of the succinate dehydrogenase/respiratory Complex II enzyme in Pseudomonas putida KT2440. SdhD is a multi-pass inner-membrane protein that helps anchor the SdhAB catalytic head to the plasma membrane and contributes to quinone-linked electron transfer through the SdhC/SdhD membrane domain. It binds heme together with the second transmembrane subunit and supports the succinate-to-fumarate TCA-cycle step carried out by the SdhABCD complex.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005886 plasma membrane | IEA GO_REF:0000120 | ACCEPT | Summary: Correct localization for the bacterial inner-membrane succinate dehydrogenase anchor subunit. Reason: UniProt annotates SdhD as a cell inner membrane, multi-pass membrane protein. In Gram-negative bacteria the inner membrane corresponds to the GO plasma membrane. Supporting Evidence: file:PSEPK/sdhD/sdhD-uniprot.txt SUBCELLULAR LOCATION: Cell inner membrane |
| GO:0006099 tricarboxylic acid cycle | IEA GO_REF:0000120 | ACCEPT | Summary: Correct TCA-cycle annotation because SdhD is part of the SdhABCD succinate dehydrogenase complex. Reason: The SdhABCD complex catalyzes the succinate-to-fumarate step of the TCA cycle. SdhD is not the catalytic flavoprotein subunit, but it is part of the required membrane anchor/quinone-transfer domain of the same complex. Supporting Evidence: file:PSEPK/sdhD/sdhD-uniprot.txt PATHWAY: Carbohydrate metabolism; tricarboxylic acid cycle. |
| GO:0009055 electron transfer activity | IEA GO_REF:0000118 | ACCEPT | Summary: Correct subunit-level role for the heme/quinone membrane domain of succinate dehydrogenase. Reason: SdhD is a membrane anchor subunit with heme and ubiquinone-binding features, contributing to electron transfer from the catalytic head to the quinone pool. Supporting Evidence: file:PSEPK/sdhD/sdhD-uniprot.txt Name=heme; Xref=ChEBI:CHEBI:30413; |
| GO:0009060 aerobic respiration | IEA GO_REF:0000118 | ACCEPT | Summary: Correct respiratory context for the forward succinate dehydrogenase complex. Reason: SdhD is part of membrane-bound succinate dehydrogenase/Complex II, coupling TCA-cycle succinate oxidation to aerobic respiratory electron transfer. |
| GO:0016020 membrane | IEA GO_REF:0000120 | MODIFY | Summary: Correct but less precise than the plasma membrane/inner membrane annotation. Reason: SdhD is a membrane protein, but UniProt specifies the bacterial cell inner membrane and GOA already has the more informative plasma membrane annotation. Use GO:0005886 as the preferred location term. Proposed replacements: plasma membrane Supporting Evidence: file:PSEPK/sdhD/sdhD-uniprot.txt SUBCELLULAR LOCATION: Cell inner membrane |
| GO:0017004 cytochrome complex assembly | IEA GO_REF:0000118 | REMOVE | Summary: Over-propagated assembly-process annotation; SdhD is a cytochrome/heme-containing subunit, not an assembly factor. Reason: UniProt supports SdhD as a membrane-anchoring subunit of succinate dehydrogenase with heme binding, but not as a factor that assembles cytochrome complexes. The annotation appears to over-interpret cytochrome b/heme membership as an assembly process. |
| GO:0020037 heme binding | IEA GO_REF:0000120 | ACCEPT | Summary: Correct heme-binding feature for the SdhC/SdhD membrane anchor domain. Reason: UniProt annotates heme for SdhD and states that the heme is bound between the two transmembrane subunits. This is a meaningful molecular feature of the Complex II membrane domain. Supporting Evidence: file:PSEPK/sdhD/sdhD-uniprot.txt Name=heme; Xref=ChEBI:CHEBI:30413; |
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Download this section (compressed HTML)Q: Does the SdhC/SdhD membrane domain of P. putida KT2440 bind heme stoichiometrically and what quinone species is preferred in vivo?
Experiment: Purify SdhABCD and measure heme content, quinone binding, and succinate:quinone activity after mutating the predicted SdhD heme and ubiquinone-binding residues.
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