Mitochondrial carriers of Ustilago maydis and Aspergillus terreus involved in itaconate production: same physiological role but different biochemical features

Itaconic acid (IA) is a naturally occurring dicarboxylic acid with applications in the manufacture of polymers. IA can be produced by fermentation using the fungi Aspergillus terreus or Ustilago maydis as biocatalysts. Indirect evidence has suggested that the mitochondrial carriers Ustilago maydis Um_Mtt1 and Aspergillus terreus At_MttA export mitochondrially synthesized cis-aconitate to the cytosol for IA synthesis using malate as a counter-substrate. Here, by assaying the transport features of recombinant Um_Mtt1 and At_MttA in reconstituted liposomes, we find that both proteins efficiently transport cis-aconitate, but malate is well transported only by Um_Mtt1 and 2-oxoglutarate only by At_MttA. Bioinformatic analysis shows that Um_Mtt1 and At_MttA form a distinctive mitochondrial carrier subfamily. Our data show that, although fulfilling the same physiological task, Um_Mtt1 and At_MttA have different biochemical features.