SOD2 V16A associates with complex IV of the mitochondria respiration chain, resulting in decreased complex IV activity and basal respiration in human arterial pulmonary endothelial cells. (A) Electron microscopy images of APEX-fused SOD2 variants obtained at ×100 000 magnification with JEM 1400Plus transmission electron microscope. (B-C) Western blots and quantification of mitochondria respiration chain complexes in SOD2 variants. (D-E) Western blots and fold enrichment calculations of APEX-fused SOD2 variants after biotinylating and streptavidin pulldown. (F) Enzymatic activities of complexes I, III, and IV in SOD2 variants normalized to complex V activity. (G) Mitochondria respiration of cells transduced with either SOD2 variant. Results are given in mean with standard deviation.