title: Evolution of the Isd11-IscS complex reveals a single alpha-proteobacterial endosymbiosis for all eukaryotes.
abstract: Giardia and Trichomonas are eukaryotes without standard mitochondria but contain mitochondrial-type alpha-proteobacterium-derived iron-sulfur cluster (ISC) assembly proteins, located to mitosomes in Giardia and hydrogenosomes in Trichomonas. Although these data suggest a single common endosymbiotic ancestry for mitochondria, mitosomes, and hydrogenosomes, separate origins are still being proposed. Here, we present a bioinformatic analysis of Isd11, a recently described essential component of the mitochondrial ISC assembly pathway. Isd11 is unique to eukaryotes but functions closely with the alpha-proteobacterium-derived cysteine desulfurase IscS. We demonstrate the presence of homologues of Isd11 in all 5 eukaryotic supergroups sampled, including hydrogenosomal and mitosomal lineages. The eukaryotic invention of Isd11 as a functional partner to IscS directly implies a single shared alpha-proteobacterial endosymbiotic ancestry for all eukaryotes. This pinpoints the alpha-proteobacterial endosymbiosis to before the last common ancestor of all eukaryotes without ambiguity.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Richards
authors.forename: Mark
authors.initials: M
authors.lastname: van der Giezen
mesh_terms: D020561:Alphaproteobacteria / Q000235:genetics* / Q000254:growth & development; D000595:Amino Acid Sequence; D013437:Carbon-Sulfur Lyases / Q000235:genetics; D005057:Eukaryotic Cells / Q000378:metabolism* / Q000382:microbiology; D019143:Evolution, Molecular; D007506:Iron-Sulfur Proteins / Q000235:genetics*; D024101:Mitochondrial Proteins / Q000235:genetics*; D008954:Models, Biological; D008969:Molecular Sequence Data; D010802:Phylogeny; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D013559:Symbiosis / Q000235:genetics*
chemical_list: D007506:Iron-Sulfur Proteins; C508374:Isd11 protein, S cerevisiae; D024101:Mitochondrial Proteins; D029701:Saccharomyces cerevisiae Proteins; D013437:Carbon-Sulfur Lyases; C080546:cysteine desulfurase