A 2[4Fe-4S] Ferredoxin is substrate of Ferredoxin-NADP+ Reductase from Leptospira interrogans

ARLETH LOPEZ RIVERO; MATIAS MUSUMECI; EDUARDO CECCARELLI; DANIELA CATALANO DUPUY*

San Luis

Congreso; 47 Annual Meeting Argentine Society for Biochemistry and Molecular Biology; 2011

Argentine Society for Biochemistry and Molecular Biology

Ferredoxins (Fds) are small iron-sulfur proteins with low redox potential which act as electron donors in various metabolic pathways. They can be grouped in three distinct families, the plant and mammalian type [2Fe?2S], the thioredoxin-like [2Fe-2S] and the 2[4Fe-4S] ferredoxins, first isolated from anaerobic bacteria. The latter may differ in cluster type (3Fe or 4Fe), number (one or two), and length of polypeptide chain. Ferredoxins can be substrates of ferredoxin-NADP+ reductases (FNR) in redox metabolisms in mitochondria, plastids and bacteria. We have identified and cloned a 2[4Fe-4S] ferredoxin (LFd2) from Leptospira interrogans, a parasitic bacterium of animals and humans. We succeeded in expressing and purifying the recombinant protein with its Fe-S cluster properly bound by co-expressing the biogenesis iron-sulfur system (ISC) from Escherichia coli. An O2-free atmosphere was required during the purification protocol. LFd2 displayed spectral similarities with typical 2[4Fe-4S] ferredoxins. We were able to measure cytochrome c reductase activity with L. interrogans FNR and LFd2. Our results suggest that electron transfer between the reductase and LFd2 is optimal at pH 6,5 and low salt concentration. Our studies show that in L. interrogans a plastidic type FNR exchanges electrons with a bacterial type ferredoxin, process which has not been previously observed in nature.