Mitochondrion is a central organelle for formation of cellular FeS clusters. This function is mediated by iron-sulfur cluster (ISC) assembly machinery that was inherited from #-proteobacterial ancestor of mitochondria. Surprisingly, in Entamoeba histolytica and its free- living relative Mastigamoeba balamuthi, the ISC machinery was replaced by #-proteobacterial NIF-like system. In M. balamuthi genome, we identified two paralogues of NifS (cysteine desulfurase) and NifU (scaffold protein). One paralogue of each protein was equipped with amino-terminal extension that targeted the protein to mitochondria (MbNifS-M, MbNifU-M), while the second paralogue was found in the cytosol (MbNifS-C, MbNifU-C). Accordingly, cysteine desulfurase activity was detected in both cytosol and organellar fractions of M. balamuthi. Dual localization of NIF system corresponded to the dual localization of FeS proteins (hydrogenase, pyruvate:ferredoxin oxidoreductase). Entamoeba possessed only single EhNifS and EhNifU that we identified in cytosol, but not in mitosomes, reduced forms of mitochondria. Our results suggest that M. balamuthi acquired the genes for NifS and NifU from the bacterial donor. Both genes were duplicated and destined to function in the cytosol and in mitochondria, where they replaced the original eukaryotic ISC machinery. The mitochondrial form of NIF machinery was most likely lost in Entamoeba.
Support:
| overview of annotation of the best candidates (blastx against nr) | |
|---|---|
| best candidate transcripts | 28060 |
| no hit to nr | 2418 |
| hit, but annotation mising | 4438 |
| best hit with bit score >100 | 14105 |
| best hit with bit score >100 and covers >80% of the protein
(a.k.a. complete transcripts) | 3174 |
| number of transcript which have the same best hit | 19819 |
| transcripts not mapped to genome v41 | 1264 |
table of blastx against NCBI nr: best_hits.tsv