Fig. 4: Structure of the SDHA-AF2-AF4 complex. | Nature Communications

Fig. 4: Structure of the SDHA-AF2-AF4 complex.

From: Disordered-to-ordered transitions in assembly factors allow the complex II catalytic subunit to switch binding partners

Fig. 4

a Ribbon diagram of the human SDHA-AF2-AF4 complex. SDHA is shown in gray, SDHAF2 is shown in cyan, and SDHAF4 is shown in orange. The covalent FAD is shown as a stick representation with carbons yellow, oxygens red, nitrogens blue, and phosphorous orange. The isoalloxazine functional group of the FAD is positioned between the flavin-binding ___domain of SDHA and the C-terminus of SDHAF4. Key interactions are shown in the inset. b Orientation of SDHAF2 and SDHAF4 in the complex. SDHA is shown as ribbons and SDHAF2 and SDHAF4 are shown as space-filling. The view is rotated 70° around the x-axis as compared to the view in (a). c Interactions between the C-terminus of SDHAF4 and the SDHA active site. The position of the conserved C-terminus is stabilized by interactions between SDHAF4D107 and SDHAF4F108 and SDHA active site residues SDHAR451 and SDHAH407. d Validation of SDHAF4 binding residues using mutagenesis. SDHAF4 containing the indicated C-terminal mutations was evaluated for the ability to displace SDHAF2 from the SDHA-AF2 complex. The assembly factors that remained bound to SDHA were visualized after the separation of the reaction on an SDS-PAGE gel. Mutations involved SDHAF4D107 (SDHAF4D107A, SDHAF4D107T and SDHAF4D107N), and SDHAF4F108 (SDHAF4F108A and SDHAF4ΔF108). The SDS-PAGE gel is representative of n = 4 independent experiments. ImageJ quantitation of SDHAF2 (teal) and SDHAF4 (brown) was used to calculate the percentage of each assembly bound to SDHA, as compared to a control (100%). This is expressed on the y-axis of each bar graph as mean values ± SD. Bar graphs show mean values ± SD, and statistics were calculated by paired two-tailed Student’s t-test. Source data are provided as a Source Data file.

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