Antimycin A resistance in a mutant Leishmania tarentolae strain is correlated to a point mutation in the mitochondrial apocytochrome b gene

In this paper we report the first case of antimycin A resistance in a proto zoan parasite that is attributable to a mutation in the mitochondrial apocy tochrome b (CYb) gene. We selected for, and isolated, a mutant Leishmania t arentolae strain that is resistant to antimycin A. This resistance was evid ent at the levels of the in vitro growth and enzymatic activity of the cyto chrome brl complex. Molecular characterisation of the mutant revealed a Ser 35Ile mutation in the expected legion of the CYb gene. In kinetoplastids, C Yb and other structural genes of the mitochondrial genome are located on th e maxicircle component of the mitochondrial DNA, which is present in 20-50 copies. Primer-extension analysis confirmed the presence of the mutation at the mRNA level. The phenotypic manifestation of the mutation implies that the CYb mRNA is edited and translated within the mitochondrion, Thus, this finding provides direct evidence that edited RNAs are translated in kinetop lastid mitochondria. Furthermore, a defined mutation conferring drug resist ance to a mitochondrial gene product can be exploited for the development o f mitochondrial transfection systems for trypanosomatids.