a, OCR measurements in wild-type and MITOK-knockout HeLa cells treated with either vehicle or 1 pM valinomycin for 1 h. Representative of three independent experiments. b, OCR measurements in wild-type and MITOK-knockout HeLa cells transfected with control or mitoK ATP -expressing (MITOSUR-P2A-MITOK) plasmids. Representative of three independent experiments. c, Maximal cristae width in the indicated genotype. n ≥ 12 individual cells (approximately 20 cristae per cell were measured) from 2 independent preparations. *P ≤ 0.013 using two-way ANOVA with Holm–Sidak correction. d, OPA1 crosslinking (using 1 mM BMH) in wild-type and MITOK-knockout cells. Similar results were obtained in three independent experiments. e, f, Extracellular acidification rate (ECAR) (e) and OCR (f) measurements in intact cells of the indicated genotype. n = 5 biological replicates, representative of 2 independent experiments. g, ROS production during energy stress. Cells were incubated in 5.5 mM of either glucose or 2-deoxyglucose in the presence or absence of 30 μM diazoxide, and fluorescence was monitored for 16 h. Box plots indicate the rate of ROS production over this time frame. n ≥ 10 biological replicates from 3 independent experiments. *P < 0.05 using three-way ANOVA with Holm–Sidak correction. h, Cell death analysis in HeLa cells treated with 0, 100 or 500 μM H 2 O 2 . Data are normalized to the untreated condition, and expressed as mean ± s.d. n = 3 independent experiments. *P < 0.003 using two-way ANOVA with Holm–Sidak correction. Source data