Extended Data Fig. 7: Differential growth complementation of human LIAS-containing Gal-YAH1-lip5Δ cells by human FDX1 and FDX2 reflects their distinct functions.

Gal-YAH1-lip5Δ yeast cells were transformed with a plasmid encoding human LIAS plus vectors containing no gene (-), FDX1 and/or FDX2 as indicated. a Cells were grown in liquid media for 4 days. Optical density (OD) at 600 nm was measured every 30 min. Growth in minimal lactate medium (SLac) is indicated by dashed lines, in rich yeast peptone lactate (YPLac) medium by solid lines. Grey dashed lines indicate standard errors (n = 4) using a microplate reader. b Serial dilutions of the indicated yeast strains were spotted onto agar plates containing minimal (S) or yeast peptone rich (YP) medium plus the indicated carbon sources. Plates were incubated at 30 °C for 3 days. The growth results fit to distinct functions of human FDX1 and FDX2 in lipoylation/heme a synthesis and Fe/S protein biogenesis, respectively. Complementation of the LIAS-expressing Gal-YAH1-lip5Δ cells with FDX2 but not FDX1 supported growth due to Fe/S protein biogenesis restoration. The residual growth on non-fermentable carbon sources (lactate or glycerol) was due to the leaky GAL promoter allowing residual amounts of Yah1, and hence lipoate/heme a, being produced. Growth under these conditions was increased to normal levels by the combined expression of both human FDXs because FDX1 regenerated synthesis of both lipoate and heme a, and FDX2 supported Fe/S protein biogenesis.