Searching the structural grounds for high catalytic efficiency of plastidic type Ferredoxin-NADP(H) reductases: the structure of L. interrogans enzyme.

CATALANO DUPUY, DANIELA L.; NASCIMENTO, ALESSANDRO S.; BERNARDES, AMANDA; DE OLIVEIRA NETO, MARIO; SANTOS, MARÍA AUXILIADORA M; POLIKARPOV, IGOR; CECCARELLI, EDUARDO A.

Montevideo, URUGUAY

Conferencia; 6th International Conference of Biological Physics (ICBP); 2007

International Union of Pure and Applied Physics (IUPAP), International Union for Pure and Applied Biophysics (IUPAB), Federación Iberoamericana de Sociedades de Física (FEIASOFI) and related Societies

Ferredoxin-NADPH(H) reductases (FNRs) are flavoenzymes that catalyze the electron transfer between NADP(H) and the proteins ferredoxin or flavodoxin. A number of structural features distinguish plant and bacterial FNRs, one of which is the mode of the cofactor FAD binding. Leptospira interrogans is a spirochaete parasitic bacterium capable of infecting humans and mammals in general. Surprisingly, we have previously found that Leptospira interrogans FNR (LepFNR) belongs to the plastidic class of FNRs at variance of all other bacterial enzymes. We solved the crystal structures of LepFNR and the complex of the protein with its natural substrate NADP+. LepFNR displays an important divergence at primary structure level with respect to other reductases of the plastidic class (only a 35% amino-acid sequence identity with maize-root FNR). However, the comparison of the solved structures with those of known FNRs reveals significant structural similarities of the enzyme with the plant but not with the bacterial FNRs. Our small angle X-ray scattering experiments also show that opposite to Plasmodium falciparum FNR that is capable of a covalent dimer formation, LepFNR in solution is a monomeric enzyme. Moreover, our biochemical data demonstrate that the LepFNR has an enzymatic activity similar to those reported for the plastidic enzymes and is significantly different from bacterial flavoenzymes, which display lower turnover rates. The typical structural and biochemical characteristics of plants FNRs revealed for LepFNR support the notion of a putative lateral gene transfer which presumably offers Leptospira interrogans evolutionary advantages. The wealth of structural information about LepFNR provides molecular basis for advanced drugs developments against leptospirosis.