Protein–protein interaction studies provide evidence for electron transfer from ferredoxin to lipoic acid synthase in Toxoplasma gondii

• Recombinant lipoate synthase from the parasite Toxoplasma gondii is likely monomeric.
• Protein–protein interaction with plant-type ferredoxin is shown in two-hybrid systems.
• Reduced ferredoxin can thus be considered as electron donor to lipoate synthase.

The only known redox system in the apicoplast, a plastid-like organelle of apicomplexan parasites, is ferredoxin and ferredoxin-associated reductase. Ferredoxin donates electrons to different enzymes, presumably including lipoate synthase (LipA), which is essential for fatty acid biosynthesis. We recombinantly expressed and characterized LipA from the protozoan parasite Toxoplasma gondii, generated LipA-specific antibodies and confirmed the apicoplast localization of LipA. Electron transfer from ferredoxin to LipA would require direct protein–protein interaction. Such a robust interaction between the two proteins was demonstrated in both yeast and bacterial two-hybrid systems. Taken together, our results provide strong evidence for a role of ferredoxin as an electron donor to LipA.