The proteome of mammalian mitochondria carries a tissue-specific signature that confer these organelles the capacity to fulfill the most diverse cellular requirements. Indeed, not only has quantitative proteomics evidenced that some mitochondrial proteins are tissue-specific but also that the abundance of mitochondrial proteins is very dependent on the cell-type. In this context, discovering the molecular characteristics that make mitochondria able to sustain diverse metabolic requirements is particularly interesting in those issues and organs that maintain and regulate the body mechanism, such as the adipose tissue. It is also widely accepted that the metabolic features of cells in living organisms can differ considerably from those of immortalized cultered cells.
Therefore, we have applied mass spectrometry-based in vivo proteomics to produce the in vivo quantitative profiles of 978 proteins from mitochondria of the murine brown and white adipocyte mature adipocytes using SILAC-labelled adipocytes as internal standard for the quantitation. Our study shows that mitochondrial pathways are modeled to meet different energy demands. For the first time it has been possible to identify all the proteins that contribute to the unique metabolic features of brown adipocyte mitochondria and make them "fat burner" organelles.