Iron-sulfur subunit of the membrane-bound succinate dehydrogenase/respiratory Complex II enzyme in Pseudomonas putida KT2440. SdhB transfers electrons from the SdhA flavoprotein catalytic subunit through iron-sulfur clusters toward the membrane anchor/quinone site, contributing to quinone-linked succinate oxidation. This places SdhB at the interface between the tricarboxylic acid cycle and the aerobic respiratory electron transport chain.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0006099 tricarboxylic acid cycle | IEA GO_REF:0000002 | ACCEPT | Summary: Correct process annotation for the succinate-to-fumarate step of the TCA cycle. Reason: SdhB is part of the succinate dehydrogenase complex that oxidizes succinate to fumarate in the TCA cycle. UniProt places Q88FA8 in the bacterial route from succinate to fumarate, and the PSEPK pathway report identifies the complete sdhCDAB operon as covering step 6. Supporting Evidence: file:PSEPK/sdhB/sdhB-uniprot.txt fumarate from succinate (bacterial route): step 1/1. |
| GO:0008177 succinate dehydrogenase (quinone) activity | IEA GO_REF:0000120 | ACCEPT | Summary: Correct holoenzyme activity that SdhB contributes to as the iron-sulfur electron-transfer subunit. Reason: The complete SdhABCD complex catalyzes quinone-linked succinate oxidation, and UniProt lists EC 1.3.5.1 with the reaction a quinone + succinate = fumarate + a quinol. SdhB contributes electron transfer within this complex rather than carrying the flavin active site independently. Supporting Evidence: file:PSEPK/sdhB/sdhB-uniprot.txt Reaction=a quinone + succinate = fumarate + a quinol; |
| GO:0009055 electron transfer activity | IEA GO_REF:0000002 | ACCEPT | Summary: Correct and subunit-relevant function for the SdhB iron-sulfur protein. Reason: SdhB is the iron-sulfur relay between the SdhA flavoprotein site and the membrane quinone-reduction site, so electron transfer is a meaningful subunit-level function. |
| GO:0009060 aerobic respiration | IEA GO_REF:0000118 | ACCEPT | Summary: Correct respiratory-process context for forward succinate dehydrogenase/Complex II. Reason: UniProt distinguishes aerobic succinate dehydrogenase from anaerobic fumarate reductase. SdhB is annotated as the succinate dehydrogenase iron-sulfur subunit and participates in aerobic respiratory electron transfer. Supporting Evidence: file:PSEPK/sdhB/sdhB-uniprot.txt the succinate dehydrogenase is used in aerobic growth |
| GO:0016491 oxidoreductase activity | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: Correct but broad parent of the specific succinate dehydrogenase/electron-transfer role. Reason: The SdhB-containing complex is an oxidoreductase, but GO:0008177 and GO:0009055 better capture the specific complex-level and subunit-level functions. |
| GO:0022904 respiratory electron transport chain | IEA GO_REF:0000118 | ACCEPT | Summary: Correct process annotation because Complex II feeds electrons from succinate into the quinone pool. Reason: SdhB is an electron-transfer subunit of respiratory Complex II. The complex bridges TCA-cycle succinate oxidation to the respiratory electron transport chain. |
| GO:0051536 iron-sulfur cluster binding | IEA GO_REF:0000002 | ACCEPT | Summary: Correct cofactor-binding annotation for the succinate dehydrogenase iron-sulfur subunit. Reason: UniProt annotates [2Fe-2S], [3Fe-4S], and [4Fe-4S] cofactors for Q88FA8. Iron-sulfur cluster binding is intrinsic to SdhB electron transfer. Supporting Evidence: file:PSEPK/sdhB/sdhB-uniprot.txt Name=[2Fe-2S] cluster; Xref=ChEBI:CHEBI:190135; |
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Experiment: Purify SdhABCD and assay succinate-dependent reduction of physiological and analog quinones, while mutating conserved SdhB Fe-S ligands to confirm the electron-transfer path.
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