Quinol:fumarate reductase FAD-binding subunit FrdA.

Succinate dehydrogenase membrane anchor subunit SdhD; Membrane-anchoring subunit of succinate dehydrogenase (SDH).

Succinate dehydrogenase iron-sulfur protein SdhB; Belongs to the succinate dehydrogenase/fumarate reductase iron-sulfur protein family.

Succinate dehydrogenase flavoprotein subunit SdhA; Belongs to the FAD-dependent oxidoreductase 2 family. FRD/SDH subfamily.

succinyl-CoA synthase beta subunit SucC; Succinyl-CoA synthetase functions in the citric acid cycle (TCA), coupling the hydrolysis of succinyl-CoA to the synthesis of either ATP or GTP and thus represents the only step of substrate-level phosphorylation in the TCA. The beta subunit provides nucleotide specificity of the enzyme and binds the substrate succinate, while the binding sites for coenzyme A and phosphate are found in the alpha subunit.

Periplasmic fumarate reductase FccA; Catalyzes fumarate reduction using artificial electron donors such as methyl viologen. The physiological reductant is unknown, but evidence indicates that flavocytochrome c participates in electron transfer from formate to fumarate and possibly also to trimethylamine oxide (TMAO). This enzyme is essentially unidirectional (By similarity); In the C-terminal section; belongs to the FAD-dependent oxidoreductase 2 family. FRD/SDH subfamily.

Anaerobic fumarate hydratase FumB; Catalyzes the reversible hydration of fumarate to (S)-malate. Belongs to the class-I fumarase family.

NADH-ubiquinone oxidoreductase subunit CD NuoCD; NDH-1 shuttles electrons from NADH, via FMN and iron-sulfur (Fe-S) centers, to quinones in the respiratory chain. The immediate electron acceptor for the enzyme in this species is believed to be ubiquinone. Couples the redox reaction to proton translocation (for every two electrons transferred, four hydrogen ions are translocated across the cytoplasmic membrane), and thus conserves the redox energy in a proton gradient; In the N-terminal section; belongs to the complex I 30 kDa subunit family.

succinyl-CoA synthase alpha subunit SucD; Succinyl-CoA synthetase functions in the citric acid cycle (TCA), coupling the hydrolysis of succinyl-CoA to the synthesis of either ATP or GTP and thus represents the only step of substrate-level phosphorylation in the TCA. The alpha subunit of the enzyme binds the substrates coenzyme A and phosphate, while succinate binding and nucleotide specificity is provided by the beta subunit.