1228 3 DECEMBER 2021¥VOL 374 ISSUE 6572 science.orgSCIENCE
Fig. 1. Cells deficient in O 2 reduction retain the capacity to input electrons
into the ETC.(A) Schematic depicting the electron transport chain (ETC) and the
deposition of electrons (e−) onto a terminal electron acceptor. CytC, cytochrome c.
(B) DHODH activity as determined by stable isotope tracing with 10 mM^13 C 4 -
aspartate, which generates^13 C 3 -UTP if DHODH is active. Tracing was performed for
8 hours in 143B cells treated with vehicle [dimethyl sulfoxide (DMSO)], 500 nM
antimycin, 2mM brequinar, or in combination or cultured in 1% O 2 for 24 hours
(mean ± SEM,n= 3 biological replicates per condition). *P< 0.05.Pvalues were
calculated using a two-way analysis of variance (ANOVA). (C) Immunoblot analyses of
mitochondrial proteins in wild-type (WT), UQCRC2 (complex III) knockout (KO),
and COX4 (complex IV) KO 143B cells. (D)O 2 consumption rate (OCR) of WT,
UQCRC2 KO, and COX4 KO 143B cells treated with DMSO or 500 nM antimycinRESEARCH | RESEARCH ARTICLES