(A) Aconitase activity assay from control or FXN KO K562 cells grown in 21% O2, 1% O2 or 21% O2 with 75μM FG-4592. Bar plots show mean ± SD. ****=p < 0.0001. One-way ANOVA with Bonferroni’s post-test. (B) Immunoblot of control or FXN KO cells grown in 21% O2, 1% O2 or 21% O2 with 75μM FG-4592, blotted for OXPHOS subunits or Tubulin. (C) Immunoblot of control or FXN KO cells grown in 21% O2, 1% O2 or 21% O2 with 75μM FG-4592, blotted for Lipoic acid, which is conjugated to PDH-E2, KGDH-E2 and GCSH. Additional blots against OGDH (i.e. KGDH-E1) and Actin. (D) Immunoblot of control or FXN KO cells grown in 21% O2, 1% O2 or 21% O2 with 75μM FG-4592, blotted against enzymes in the heme biosynthesis pathway- FECH and ALAD- or TOMM20. (E) Immunoblot of control or FXN KO cells grown in 21% O2, 1% O2 or 21% O2 with 75μM FG-4592, blotted against POLD1, MMS19 or Actin. See also Figure S3.