The TMD of iJC-TCRβ and the residues downstream to it are sufficient to target EGFP to mitochondria. COS-7 cells were transfected with the indicated constructs, and 24 hours later they were either incubated with MTR for 30 minutes or stained with anti-KDEL followed by anti–mouse Cy3 antibodies. The left column shows EGFP images, whereas the middle column shows the MTR or KDEL signal. The right column is the merge of the EGFP and MTR or KDEL signal. Fluorescent images were taken by confocal microscopy. All the constructs shown in panel A encode peptides that target the mitochondrion whereas panel B shows lack of such localization by a mutant lacking charged amino acids. The different constructs are described in Figure 1A. Bar, 10 μM.