(A) Control 143B cells (left panels), COX1∆ cybrids (middle panels), and COX2∆ cybrids (right panels). The right lane highlights structural subunits of CI (yellow), CIII (light green), and CIV (orange brown), and assembly factors (orange). Intensity-based absolute quantification (iBAQ) values were normalized to the sum of all control values. Top lanes indicate gel slice numbers and their relative native masses. 