Functional and evolutionary studies of the newly discovered putatively mitochondrial human peptidyl-prolyl cis/trans-isomerase Par17

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We have recently described a novel isoform of human Parvulin, a peptidyl prolyl cis/trans isomerase that is highly conserved among metazoan organisms. This elongated Parvulin called Par17 contains an N-terminal 25 amino acid extension relative to the well known Par14 protein. This extension is predicted to adopt an alpha-helical conformation by the secondary structure prediction package NPS. It is also recognized as putative mitochondrial targeting peptide by cellular localization prediction programs. We plan to investigate this N-terminal extension as mitochondrial targeting signal by in vitro uptake experiments as well as in vivo localization studies. This novel Par17 could satisfyingly explain controversially discussed localizations experiments of Parvulin proteins that were found in nuclei, cytosol and mitochondria. In addition, we want to functionally characterize Par17 as novel mitochondrial protein by DNA binding assays, co-immunoprecipitations and RNAi studies. As Par17 is encoded by the human genome, but is absent from rodent, bovine and non-mammalian genomes we want to determine when this signal peptide was acquired during evolution.