Fig. 4. Mitochondrial anchor is required for metaxin function. (A) Schematic representation indicates that metaxin is 317 aa in length, and its N-terminal extramitochondrial region (aa 1–272), transmembrane domain (TM, aa 272–294), and C-terminal region are inside the outer membrane (aa 295–317). Also shown here are the two deletion mutants of metaxin: MetaΔTM/C and MetaΔC. (B) MetaΔTM/C mutant fails to restore the sensitivity of Meta^mut cells to TNF, as assayed by annexin staining. Meta^mut cells were stably transfected with the empty vector, metaxin, MetaΔTM/C, or MetaΔC, respectively, and were treated with or without TNF. Cells were then analyzed for annexin staining using flow cytometry as above. (C) MetaΔTM/C exerts a dominant-negative effect on parental L929 cells in TNF sensitivity. (D) MetaΔTM/C expression leads to resistance to TNF-induced cell death in MCF-7.3.28 cells.