A Highlights from MBoC Selection: More than just a ticket canceller: the mitochondrial processing peptidase tailors complex precursor proteins at internal cleavage sites |
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| Authors: | Jana Friedl Michael R Knopp Carina Groh Eyal Paz Sven B Gould Johannes M Herrmann Felix Boos |
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| Institution: | Cornell University;aCell Biology, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany;bMolecular Evolution, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany;cDepartments of Biochemistry and Molecular Biology, Tel Aviv University, Tel Aviv 6997801, Israel |
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| Abstract: | Most mitochondrial proteins are synthesized as precursors that carry N-terminal presequences. After they are imported into mitochondria, these targeting signals are cleaved off by the mitochondrial processing peptidase (MPP). Using the mitochondrial tandem protein Arg5,6 as a model substrate, we demonstrate that MPP has an additional role in preprotein maturation, beyond the removal of presequences. Arg5,6 is synthesized as a polyprotein precursor that is imported into mitochondria and subsequently separated into two distinct enzymes. This internal processing is performed by MPP, which cleaves the Arg5,6 precursor at its N-terminus and at an internal site. The peculiar organization of Arg5,6 is conserved across fungi and reflects the polycistronic arginine operon in prokaryotes. MPP cleavage sites are also present in other mitochondrial fusion proteins from fungi, plants, and animals. Hence, besides its role as a “ticket canceller” for removal of presequences, MPP exhibits a second conserved activity as an internal processing peptidase for complex mitochondrial precursor proteins. |
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