A bacterial 2[4Fe4S] ferredoxin as redox partner of the plastidic-type ferredoxin-NADP+ reductase from Leptospira interrogans

• Published in: Biochimica et biophysica acta. General subjects 2019-04, Vol.1863 (4), p.651-660
• Main Authors: López Rivero, Arleth S., Rossi, Ma. Agustina, Ceccarelli, Eduardo A., Catalano-Dupuy, Daniela L.
• Format: Article
• Language: English
• Subjects: Ferredoxin; Ferredoxin-NADP+ reductase; Iron-sulfur clusters; Leptospira interrogans
• ISSN: 0304-4165; 1872-8006
• DOI: 10.1016/j.bbagen.2019.01.004

Ferredoxins are small iron-sulfur proteins that participate as electron donors in various metabolic pathways. They are recognized substrates of ferredoxin-NADP+ reductases (FNR) in redox metabolisms in mitochondria, plastids, and bacteria. We previously found a plastidic-type FNR in Leptospira interrogans (LepFNR), a parasitic bacterium of animals and humans. Nevertheless, we did not identify plant-type ferredoxins or flavodoxins, the common partners of this kind of FNR. Sequence alignment, phylogenetical analyses and structural modeling were performed for the identification of a 2[4Fe4S] ferredoxin (LepFd2) as a putative redox partner of LepFNR in L. interrogans. The gene encoding LepFd2 was cloned and the protein overexpressed and purified. The functional properties of LepFd2 and LepFNR-LepFd2 complex were analyzed by kinetic and mutagenesis studies. We succeeded in expressing and purifying LepFd2 with its FeS cluster properly bound. We found that LepFd2 exchanges electrons with LepFNR. Moreover, a unique structural subdomain of LepFNR (loop P75-Y91), was shown to be involved in the recognition and binding of LepFd2. This structural subdomain is not found in other FNR homologs. We report for the first time a redox pair in L. interrogans in which a plastidic FNR exchanges electron with a bacterial 2[4Fe4S] ferredoxin. We characterized this reaction and proposed a model for the productive LepFNR-LepFd2 complex. Our findings suggest that the interaction of LepFNR with the iron-sulfur protein would be different from the one previously described for the homolog enzymes. This knowledge would be useful for the design of specific LepFNR inhibitors. [Display omitted] •We expressed, purified and characterized a 2[4Fe4S] ferredoxin from Leptospira interrogans.•The 2[4Fe4S] ferredoxin exchanges electrons with a plastidic ferredoxin-NADP+ reductase.•Ferredoxin recognition by ferredoxin-NADP+ reductase involves a unique structural subdomain.•We found a new redox partner of the plastidic-type ferredoxin-NADP+ reductases.