A plastidic-type ferredoxin-NADP(H) reductase in the pathogen bacterium Leptospira interrogans

DANIELA L. CATALANO-DUPUY; MATÍAS A. MUSUMECI; EDUARDO A. CECCARELLI

Salta, Argentina

Congreso; 3st Latin American Protein Society Meeting; 2010

Latin American Protein Society

Ferredoxin-NADP(H) reductases (FNR) are flavoenzymes that deliver NADPH or low potential one-electron donors (ferredoxin, flavodoxin) to redox metabolisms in plastids, mitochondria and bacteria. There are differences in catalytic efficiencies among the members of the FNR family. Whereas plastidic FNRs display turnover numbers related to the needs of the photosynthesis, bacterial reductases are much less active. It is not known how this catalytic improvement was accomplished but probably was obtained by subtle changes in the protein structure and FAD conformation. We found that FNR from Leptospira interrogans (LepFNR), a parasitic bacterium of animals and humans, belongs to the plastidic class of FNRs at variance of all other FNRs found in bacteria1,2. It has occurred probably as result of a putative lateral gene transfer offering L. Interrogans evolutionary advantages. We found that LepFNR display turnover rates similar to those observed for plastidic enzymes. However, LepFNR does not show substrate promiscuity with ferredoxins from pea and Escherichia coli or bacterial flavodoxins. LepFNR is more stable than other FNRs with respect to pH changes and temperature. Denaturation by urea showed an unusual stability of the enzyme. At 8 M urea LepFNR retains 37% of the catalytic activity. FAD fluorescence and circular dichroism of the enzyme indicate the existence of a high stable protein core in agreement with the activity measurements. In silico analysis suggests that interaction between the NADP(H) and the FAD protein domains may account for the increased stability of this enzyme.