A novel two-step mechanism for removal of a mitochondrial signal sequence involves the mAAA complex and the putative rhomboid protease Pcp1.
The yeast protein cytochrome c peroxidase (Ccp1) is nuclearly encoded and imported into the mitochondrial intermembrane space, where it is involved in degradation of reactive oxygen species. It is known, that Ccp1 is synthesised as a precursor with a N-terminal pre-sequence, that is proteolytically removed during transport of the protein. Here we present evidence for a new processing pathway, involving novel signal peptidase activities. The mAAA protease subunits Yta10 (Afg3) and Yta12 (Rca1) were identified both to be essential for the first processing step. In addition, the Pcp1 (Ygr101w) gene product was found to be required for the second processing step, yielding the mature Ccp1 protein. The newly identified Pcp1 protein belongs to the rhomboid-GlpG superfamily of putative intramembrane peptidases. Inactivation of the protease motifs in mAAA and Pcp1 blocks the respective steps of proteolysis. A model of coupled Ccp1 transport and N-terminal processing by the mAAA complex and Pcp1 is discussed. Similar processing mechanisms may exist, because the mAAA subunits and the newly identified Pcp1 protein belong to ubiquitous protein families.
Esser
Karlheinz
K
Botanisches Institut der Universität Düsseldorf, Universitätsstr. 1, Germany. esserkh@uni-duesseldorf.de
Tursun
Baris
B
Ingenhoven
Martin
M
Michaelis
Georg
G
Pratje
Elke
E
D000251:Adenosine Triphosphatases / Q000378:metabolism; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001483:Base Sequence; D003578:Cytochrome-c Peroxidase / Q000378:metabolism*; D004271:DNA, Fungal / Q000235:genetics; D010450:Endopeptidases / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism; D005800:Genes, Fungal; D008666:Metalloendopeptidases / Q000737:chemistry / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D011499:Protein Processing, Post-Translational; D021382:Protein Sorting Signals / Q000235:genetics; D021122:Protein Subunits; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D004271:DNA, Fungal; D005656:Fungal Proteins; D024101:Mitochondrial Proteins; D021382:Protein Sorting Signals; D021122:Protein Subunits; D029701:Saccharomyces cerevisiae Proteins; D003578:Cytochrome-c Peroxidase; D010450:Endopeptidases; D008666:Metalloendopeptidases; C114583:m-AAA proteases; D000251:Adenosine Triphosphatases; C102166:YTA12 protein, S cerevisiae; C090045:AFG3 protein, S cerevisiae