FURTHER EVIDENCE FOR THE PRESENCE OF MITOCHONDRIALLY ENCODED SUBUNITSIN CYTOCHROME-C-OXIDASE OF THE TRYPANOSOMATID CRITHIDIA-FASCICULATA

Mitochondrial mRNAs in trypanosomatids are edited by uridylate inserti on and deletion, The respiratory chain complexes cytochrome c reductas e, cytochrome c oxidase and F0F1-ATPase of the insect trypanosomatid C rithidia fasciculata have been isolated and analysed by peptide micros equencing, but so far, proteins encoded by edited (and unedited) mitoc hondrial mRNAs have not been found. In this paper, we provide evidence that the mitochondrial mRNAs encoding the three large subunits of cyt ochrome c oxidase are indeed translated, First, purified hole cytochro me c oxidase turned out to be cysteine-rich, in agreement with the hig h cysteine codon-content of the sequence of mitochondrial cox subunit mRNAs. Second, in mass spectrometry measurements of cytochrome c oxida se, a protein was detected with the predicted molecular weight of cyto chrome c oxidase subunit 2, Finally, an antibody generated against a f usion protein produced in Escherichia coli from constructs containing a segment of cytochrome c oxidase subunit 2 cDNA, specifically recogni sed protein bands present in cytochrome c oxidase following SDS PAGE. However, these proteins were present in the high molecular weight regi on of the gel, suggesting that cytochrome c oxidase subunit 2 aggregat es in the presence of SDS.