Redox‐dependent lipoylation of mitochondrial proteins in P lasmodium falciparum

Lipoate scavenging from the human host is essential for malaria parasite survival. Scavenged lipoate is covalently attached to three parasite proteins: the H ‐protein and the E 2 subunits of branched chain amino acid dehydrogenase ( BCDH ) and α‐ketoglutarate dehydrogenase ( KDH ). We show mitochondrial localization for the E 2 subunits of BCDH and KDH , similar to previously localized H ‐protein, demonstrating that all three lipoylated proteins reside in the parasite mitochondrion. The lipoate ligase 1, LipL1 , has been shown to reside in the mitochondrion and it catalyses the lipoylation of the H ‐protein; however, we show that LipL1 alone cannot lipoylate BCDH or KDH . A second mitochondrial protein with homology to lipoate ligases, LipL2 , does not show ligase activity and is not capable of lipoylating any of the mitochondrial substrates. Instead, BCDH and KDH are lipoylated through a novel mechanism requiring both LipL1 and LipL2 . This mechanism is sensitive to redox conditions where BCDH and KDH are exclusively lipoylated under strong reducing conditions in contrast to the H ‐protein which is preferentially lipoylated under less reducing conditions. Thus, malaria parasites contain two different routes of mitochondrial lipoylation, an arrangement that has not been described for any other organism.