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. 2023 Apr 27;299(6):104761. doi: 10.1016/j.jbc.2023.104761

Figure 2.

Figure 2

Complex II in the Krebs cycle. The Krebs cycle, also called the tricarboxylic acid cycle or the citric acid cycle, is an energy-harvesting process integral to aerobic respiration. The Krebs cycle uses a series of oxidation-reduction reactions on carboxylate-containing small molecules. The Krebs cycle contributes to oxidative phosphorylation in multiple ways. First, it produces reducing equivalents in the form of NADH, which is used by respiratory complex I. Second, the chemical intermediate succinate is used by complex II to provide another conduit for electrons to enter the respiratory chain. Coordinates used to develop this figure include human pyruvate dehydrogenase (PDB 6H55, (212)), porcine citrate synthase (PDB 1CTS, (213)), porcine aconitase (PDB 7ACN, (214)), human isocitrate dehydrogenase (PDB 7CE3, (215)), porcine succinyl CoA synthase (PDB 2FP4, (216)), porcine succinate dehydrogenase (PDB 1ZOY, (75)), human fumarase (PDB 5UPP, (217)), and porcine malate dehydrogenase (PDB 1MLD, (218)). The α-ketoglutarate dehydrogenase complex was modeled from the E. coli E1 component (PDB 2JGD, (219)), the E. coli E3-binding domain (PDB 1BBL, (220)), the Thermus thermophilus E3 component (PDB 2EQ7, (221)), and the E. coli lipoyl domain (PDB 1PMR, (222)). SDH, succinate dehydrogenase.