Fig. 6: Cys⁴⁷⁷ and Cys⁴⁸⁴ sulfinamide impair DLD homodimer formation.

a Top view of dihydrolipoamide dehydrogenase (DLD_E3 dimer) in complex with the subunit binding of human dihydrolipoamide transacylase (E2b). DLD_E3 dimer is reported in gray (chain A) and blue (chain B) cartoon representation, whereas E2b is reported in pink cartoon representation. FAD and NAD+ are reported in orange and sticks representation, respectively. Residues within 4 Å from C484 are reported in white (chain A) and blue (chain B) sticks and labeled. Dashed lines indicate the inter-chain interaction between the indicated Cys³⁸⁸ and Cys⁴⁸⁴ residues. The reported distances are lower than 2.5 Å. b Residues within 4 Å from Cys⁴⁸⁴sulfinamide (sC484) are reported in white (chain A) and blue (chain B) sticks and labeled. Dashed lines indicate the inter-chain distance at the level of the indicated Cys³⁸⁸ and sCys⁴⁸⁴ residues. The reported distances are greater than 5.5 Å. c HEK293T cells were transfected with either empty vector/WT DLD/DLD C484A/DLD C484W. SDS IBs were perfomed probing for the expression tag Myc-DDK, DLD and β-actin as loading control. d Whole cells lysates where assessed for DLD dehydrogenase activity (n = 5 technical repeats). Data were analyzed by one-way ANOVA with Dunnet’s multiple comparisons test. e DLD in-gel activity assay and IBs on native gels of whole cells lysates from HEK293T transfected as in (c). f Lysates from (d) were used for kinetic assay for DLD dehydrogenase activity with increasing concentration of lipoic acid (n = 4 technical repeats). Non linear regression model of Michealis-Menten is shown, together with Lineweaver-Burk plot. All error bars display mean ± SEM. Data shown are representative of two or more independent experiments. Source data are provided as a Source Data file.