A new face on apoptosis: death-associated protein 3 and PDCD9 are mitochondrial ribosomal proteins

Tyro proteins known to be involved in promoting apoptosis in mammalian cell s have been identified as components of the mammalian mitochondrial ribosom e, Proteolytic digestion of whole mitochondrial ribosomal subunits followed by analysis of the peptides present using liquid chromatography-tandem mas s spectrometry revealed that the proapoptotic proteins, death-associated pr otein 3 (DAP3) and the programmed cell death protein 9, are both components of the mitochondrial ribosome. DAP3 has motifs characteristic of guanine n ucleotide binding proteins and is probably the protein that accounts for th e nucleotide binding activity of mammalian mitochondrial ribosomes, The obs ervations reported here implicate mitochondrial protein synthesis as a majo r component in cellular apoptotic signaling pathways. (C) 2001 Federation o f European Biochemical Societies. Published by Elsevier Science B.V. All ri ghts reserved.