Characterization and Partial Purification of tRNA Processing Activities from Potato Mitochondria

In plant mitochondria, as in most other genetic systems, several enzymatic processing and modification steps are required to yield mature tRNAs from primary transcripts. Three of the enzymes involved, RNase P, 3'-processing activity, and tRNA nucleotidyl transferase, were identified in potato (Solanum tuberosum) mitochondria and have been separated by several purification steps. RNase P was partially purified, with only a few proteins detectable in active fractions after a final glycerol gradient step. A small RNA molecule present in fractions with RNase P activity contains the heptanucleotide conserved in the other known RNase P RNA sequences and may be a fragment of the RNA moiety of the plant mitochondrial RNase P.