Kinetoplastid mitochondria contain functional tRNAs which are encoded in nuclear DNA and also contain small mlnltircJe and maxicircle transcripts of unknown function

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Abstract
The mitochondrion of Leishmania tarentolae contains approximately 35-40 tRNAs, many of which comigrate with cytoplasmic tRNAs. Both mitochondrial (KtRNA) and cytoplasmic (CtRNA) tRNAs are functional, as they could be acylated either by mitochondrial or cytoplasmic synthetase extracts. There are two methionyl tRNA species in the cytoplasmic and mitochondrial fractions, one of which is unique to each fraction, indicating that the KtRNA fraction is free of CtRNA contamination. Leucyl and glycyl tRNAs were identified by hybridization with a genomic clone from Trypanosoma brucei. KtRNA hybridizes with nuclear chromosomes, but with minicircle or maxicircle DNA. KtRNA isolated by DEAE chromatography or agrose gel electrophoresis contains additional small RNAs which hybridize with both minicircle and maxicircle DNA. The transcripts do not migrate like tRNAs in acrylamide gels and their function is unknown. We suggest that most if not all mitchondrial tRNAs in L. tarentolae are nuclear-encoded and imported into the mitochondrion.