A Thioredoxin-like [2Fe-2S] ferredoxin from Leptospira interrogans

CATALANO DUPUY, DANIELA L; RÚA, MELINA; CECCARELLI, EDUARDO A

Tucumán, Argentina

Congreso; XLV Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular.; 2009

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Ferredoxins (Fds) are small soluble iron-sulfur proteins. Most of them are low-potential electron carriers that were long believed to consist of two phylogenetically distinct families: the [2Fe-2S] plant or [4Fe-4S] bacterial type Fds. The existence of a third family was initially suggested by the primary structure of a [2Fe-2S] protein from Clostridium pasteurianum, and was later confirmed by the crystal structure of a homologous protein from Aquifex aeolicus. The latter Fd displays a fold similar to that of thioredoxin. While homologous domains in large redox enzymes most likely function as electron carriers, the role of theses thioredoxin-like Fds is unknown. A different type of activity, perhaps a regulatory one, may be suggested by the very stable dimeric structure of these proteins, which is quite unusual among electron carriers.  We have identified and cloned a ferredoxin from Leptospira interrogans (LFd1), a parasitic bacterium of animals and humans. By co-expressing chaperons we succeeded in expressing and purifying the recombinant protein in E. coli with its Fe-S cluster properly bound. LFd1 displayed sequence and spectral similarities with thioredoxin-like Fds. By modeling in silico we predicted its probable 3D structure, which showed high similarity to A. aeolicus Fd4. We also determined that the protein is a dimer as was suggested for the A. aeolicus homologous protein.