Characterization of two nuclear-encoded protein components of mitochondrial ribonucleoprotein complexes from...

Two mitochondrial proteins with molecular masses of 18 and 51 kDa were isolated from Leishmania tarentolae, and N-terminal amino-acid sequences were obtained. The cDNAs and genes encoding these proteins were cloned using RT-PCR. The proteins were identified as components of the previously characterized mitochondrial ribonucleoprotein complexes, T-Ia and T-VI, by comigration in native gels. The p18 and p51 genes contain 17 and 9-amino-acid N-terminal sequences, which are not present in the mature proteins and may represent cleavable mitochondrial targeting sequences. There are two identical p18 genes separated by 1.7 kb in tandem array and both are transcribed. The p18 amino-acid sequence is not similar to any sequence in the database. Antiserum to p18 expressed in Escherichia coli reacts with the entire tubular mitochondrion. The p51 gene is single copy, and the amino-acid sequence is similar to mitochondrial aldehyde dehydrogenases from other organisms. The N-terminal amino-acid sequences of 71 and 62-kDa mitochondrial proteins which co-migrated in native gels with several other T-complexes were also obtained. The p71 sequence proved to be similar to hsp70 sequences from other organisms. The p62 sequence was identical to an hsp60 sequence from Trypanosoma brucei.