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

CATALANO DUPUY, D. L.; NASCIMENTO, A. S.; BERNARDES, A.; DE OLIVEIRA NETO, M; SANTOS, M.A.; POLIKARPOV, I.; CECCARELLI, E. A.

Montevideo, Uruguay

Congreso; 6th International Conference on Biological Physics and the 5th Southern Cone Biophysics Congress; 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 theelectron transfer between NADP(H) and the proteins ferredoxin orflavodoxin. A number of structural features distinguish plant andbacterial FNRs, one of which is the mode of the cofactor FAD binding.Leptospira interrogans is a spirochaete parasitic bacterium capable ofinfecting humans and mammals in general. Surprisingly, we havepreviously found that Leptospira interrogans FNR (LepFNR) belongs to theplastidic class of FNRs at variance of all other bacterial enzymes.  Wesolved the crystal structures of LepFNR and the complex of the proteinwith its natural substrate NADP+. LepFNR displays an importantdivergence at primary structure level with respect to other reductasesof the plastidic class (only a 35% amino-acid sequence identity withmaize-root FNR). However, the comparison of the solved structures withthose of known FNRs reveals significant structural similarities of theenzyme with the plant but not with the bacterial FNRs. Our small angleX-ray scattering experiments also show that opposite to Plasmodiumfalciparum FNR that is capable of a covalent dimer formation, LepFNR insolution is a monomeric enzyme. Moreover, our biochemical datademonstrate that the LepFNR has an enzymatic activity similar to thosereported for the plastidic enzymes and is significantly different frombacterial flavoenzymes, which display lower turnover rates.   Thetypical structural and biochemical characteristics of plants FNRsrevealed for LepFNR support the notion of a putative lateral genetransfer which presumably offers Leptospira interrogans evolutionaryadvantages. The wealth of structural information about LepFNR providesmolecular basis for advanced drugs developments against leptospirosis.