Protein characteristic of the hydrogenosome, a redox organelle of anaerobic unicellular eukaryotes which contains hydrogenase and produces hydrogen and ATP by glycolysis. They are found in various unrelated eukaryotes, such as anaerobic flagellates, chytridiomycete fungi and ciliates. Most hydrogenosomes lack a genome, but some like that of the anaerobic ciliate Nyctotherus ovalis, have retained a rudimentary genome.
