MitoP2, an integrated database for mitochondrial proteins.

The impact of mitochondria on several fundamental cellular processes is reflected in their involvement in the pathophysiology of common diseases such as Parkinson's disease, diabetes, and obesity and a wide range of monogenic disorders primarily associated with energy impairment or metabolic diseases. The importance of mitochondria is also reflected by the steep increase of proteins, which has been localized to this organelle. In yeast, more than 500 of the expected 700-800 mitochondrial proteins are already annotated. In the mammalian species, the expected numbers are estimated to be in the range of 1500-2000 proteins, and the currently annotated entries reach almost 700. In addition to the studies dealing with single proteins, there are many high-throughput approaches that improve the description of the mitochondrial proteome. They include computational predictions of signaling sequences, proteome mapping, mutant screening, expression profiling, protein-protein interaction, and cellular sublocalization studies. The MitoP2 database (http://www.mitop2.de/) was established to structure, explore, and customize the available data on mitochondrial proteins, functions, and diseases. MitoP2 provides a comprehensive picture of the mitochondrial proteome by focusing on (1) the orthology between species, including Saccharomyces cerevisiae, mouse, humans, and Arabidopsis thaliana; (2) the definition of mitochondrial reference sets in these species; (3) the integration of data predictive for mitochondrial localization or function stemming from genomewide approaches; (4) the allocation of a gateway for functional data from model systems and genetics of mitochondriopathies; and (5) the calculation of a combined score for each protein summarizing the indirect evidence for a mitochondrial localization. All data are accessible via search tools and linked to the original data source. By providing an overview of functional annotations from different databases, the MitoP2 database lends itself to genetic investigations of human mitochondriopathies.