THE HYDROGENOSOMAL MALIC ENZYME FROM THE ANAEROBIC FUNGUS NEOCALLIMASTIX-FRONTALIS IS TARGETED TO MITOCHONDRIA OF THE METHYLOTROPHIC YEAST HANSENULA-POLYMORPHA

Hydrogenosomal proteins always contain an amino-terminal extension whi ch is believed to be a hydrogenosomal targeting signal. In the anaerob ic fungus Neocallimastix frontalis these putative targeting signals ar e 27 amino acids long, are enriched in Ala, Leu, Ser and Arg, and have an Arg at position -2 relative to amino-acid 1 of the mature protein. These features are typically observed in mitochondrial targeting sign als. Here we show that the 27 amino-acid leader sequence of the hydrog enosomal malic enzyme of N. frontalis was capable of targeting the enz yme to mitochondria of the methylotrophic ascomycete yeast Hansenula p olymorpha. The same protein without this leader sequence remained cyto solic. These data suggest a close relationship between the protein imp ort machineries of mitochondria and hydrogenosomes in fungi and provid e further support for the notion that these two organelles share a com mon evolutionary origin.