Effects of hydrophobic residue mutation in NDUFV2 MTS on mitochondrial targeting. (a) The sites of hydrophobic residue in NDUFV2 N-terminal 1-32 amino acids were underlined and marked. (b) The effect of hydrophobic residue mutation within the N-terminal region of NDUFV2 on mitochondrial targeting. A series of point mutations targeting at hydrophobic residues were introduced into NDUFV2 with the c-myc epitope tag and expressed in T-REx-293 cells. The expressed proteins with hydrophobic residue mutations were labeled by an anti-c-myc-FITC antibody in transfected cells (green color), mitochondria were labeled by Mito Tracker Red (red color), and colocalization of expressed protein and mitochondria is shown as a merged image and indicated by yellow signals. The number of (+) symbols indicates that the proportion of cells exhibiting FITC fluorescence have a typical punctuated staining pattern and mitochondrial colocalization. The (++++) symbol indicates all of the FITC fluorescence signals in transfected cells are fully colocalized with mitochondria. The (-) symbol indicates that there is no cell producing FITC fluorescence within the mitochondrial compartment. Scale bars = 10 μ m.