Characterisation of the SUF FeS cluster machinery in the amitochondriate eukaryote Monocercomonoides exilis

Abstract

Monocercomonoides exilis is the first eukaryotic organism described as a complete amitochondriate,24 yet it shares common features with heterotrophic anaerobic/microaerophilic protists, some of which25 bear divergent mitochondrion-related organelles or MROs. It has been postulated that the retention26 of these organelles stems from their involvement in the assembly of essential cytosolic and nuclear27 FeS proteins, whose maturation requires the evolutionarily conserved mitochondrial ISC and28 cytosolic CIA machineries. The amitochondriate M. exilis lacks genes encoding the ISC machinery29 yet contains a bacteria-derived SUF system (MeSuf), composed of the cysteine desulphurase SufS30 fused to SufD and SufU, as well as the FeS scaffolding components MeSufB and MeSufC. Here, we31 show that expression of the M. exilis SUF genes, either individually or in tandem, can restore the32 maturation of the FeS protein IscR in the Escherichia coli double mutants of sufS iscS and sufB33 iscUA.