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

Figure 3.

Figure 3

Stable complexes that contain complex II subunits. Complex II subunits have been shown to functionally integrate into alternative species. A, complex II-low is a heterogeneous mixture of species that contain SDHA, SDHAF2, and SDHAF4 that runs as a broad band on a native gel (21). The predominant species is likely the stable SDHA-AF2 complex (PDB 6VAX, (140, 142)). However, it cannot be excluded that complex II-low contains SDHA-AF2-AF4 (PDB 8DYD (140)) or SDHA-AF4 (PDB 8DYE (140)). B, the SDHB subunit forms complexes with TRAP1, which may have implications for regulating cancer metabolism (PDB 7KCM (133)). C, the SDHC subunit and an SDHD paralog called Tim18 (36% identical, 57% similar) form part of the mitochondrial inner membrane protein importer, TIM22 (22). The left panel shows the experimental structure, while the right panel shows a model with this docked to SDHA and SDHB subunits. Although sterics suggest that this complex could theoretically form, functional studies suggest that the Tim18 cannot support succinate-dependent respiration and SDHD cannot support TIM22 transport activity (22, 26). SDH, succinate dehydrogenase; SDHAF, succinate dehydrogenase assembly factor.