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

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

San Miguel de Tucumán, Tucumán

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 ofthem are low-potential electron carriers that were long believed toconsist of two phylogenetically distinct families: the [2Fe-2S] plantor [4Fe-4S] bacterial type Fds. The existence of a third family wasinitially suggested by the primary structure of a [2Fe-2S] proteinfrom Clostridium pasteurianum, and was later confirmed by thecrystal structure of a homologous protein from Aquifex aeolicus.The latter Fd displays a fold similar to that of thioredoxin. Whilehomologous domains in large redox enzymes most likely functionas electron carriers, the role of theses thioredoxin-like Fds isunknown. A different type of activity, perhaps a regulatory one, maybe suggested by the very stable dimeric structure of these proteins,unusual among electron carriers.We have identified and cloned a ferredoxin from Leptospirainterrogans (LFd1), a parasitic bacterium of animals and humans.By co-expressing chaperons we succeeded in expressing andpurifying the recombinant protein in E. coli with its Fe-S clusterproperly bound. LFd1 displayed sequence and spectral similaritieswith thioredoxin-like Fds. By modeling in silico we predicted itsprobable 3D structure, which showed high similarity to A. aeolicusFd4. We also determined that the protein is a dimer as was suggestedfor the A. aeolicus homologous protein.