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Identification and analysis of novel mitochondrial proteins encoded by
small open reading frames



Mitochondria are essential organelles with crucial roles in cellular energy metabolism, cofactor biogenesis, signaling and programmed cell death. Mitochondria possess a remarkably high content of small proteins compared to other cellular compartments. About one third of the cellular proteins ≤15 kDa characterized to date are located in mitochondria. Functional examples of such small proteins cover the whole mitochondrial biology like cristae morphology, Fe-S cluster formation, metabolite transport, protein biogenesis and respiration. However, the intracellular localization and function of most small proteins is unknown. These small proteins constitute one third of the uncharacterized open reading frames in the model organism budding yeast. Taken together we predict that more than 10% of the mitochondrial proteome deserves to be discovered. In an initial study, we demonstrated the mitochondrial localization of several uncharacterized small open reading frame (smORF) proteins.

Due to their important function in the cellular energy metabolism, mitochondria are considered as the cellular power stations. Mitochondria convert the energy from nutrition to generate more than 90% of the cellular adenosine triphosphate (ATP), which is the major driver for the cellular metabolism. Mitochondrial protein dysfunctions causes severe encephalomyopathy often associated with multiple organ dysfunction and neurodegenerative diseases.

To understand mitochondrial functions, it is absolutely crucial to identify the mitochondrial protein composition. MITOsmORFs aims to identify over 100 novel mitochondrial proteins. In addition, MITOsmORFs will determine the submitochondrial localization and the functional role of mitochondrial proteins. This includes interaction mapping and characterization of mitochondrial activities in vivo and in organello to explore the unknown biology mitochondrial proteins.



  • Stiller SB, Höpker J, Oeljeklaus S, Schütze C, Schrempp SG, Vent-Schmidt J, Horvath, SE, Frazier AE, Gebert N, van der Laan M, Bohnert M, Warscheid B, Pfanner N, and Wiedemann N: Mitochondrial OXA translocase plays a major role in biogenesis of inner-membrane proteins. Cell Metab, 2016; 23 : 901-908.
  • Ellenrieder L, Opalinski L, Becker L, Krüger V, Mirus O, Straub SP, Ebell K, Flinner N, Stiller SB, Guiard B, Meisinger C, Wiedemann N, Schleiff E, Wagner R, Pfanner N, Becker T: Separating mitochondrial protein assembly and endoplasmic reticulum tethering by selective coupling of Mdm10. Nat Commun, 2016; 7 : 13021.
  • Straub SP, Stiller SB, Wiedemann N, Pfanner N: Dynamic organization of the mitochondrial protein import machinery. Biol Chem, 2016; epub June 11, 2016, doi: 10.1515/hsz-2016-0145.
  • Yofe I, Weill U, Meurer M, Chuartzman S, Zalckvar E, Goldman O, Ben-Dor S, Schütze C, Wiedemann N, Knop M, Khmelinskii A, Schuldiner M: One library to make them all: streamlining the creation of yeast libraries via a SWAp-Tag strategy. Nat Methods, 2016; 13 : 371-378.