Kinetic and structural study of the ferredoxin-NADP+ reductase from Xanthonomas citri.

TONDO, M. L.; MUSUMECI, M. A.; CECCARELLI, E. A.

San Miguel de Tucumán, Tucumán

Congreso; XLV Reunión Anual de la Sociedad Argentina de investigación en Bioquímica y Biología Molecular (SAIB); 2009

Sociedad Argentina de investigación en Bioquímica y Biología Molecular (SAIB)

Ferredoxin-NADP(H) reductases (FNRs) are FAD-containingmonomeric enzymes that deliver NADPH or low potential oneelectrondonors (ferredoxin, flavodoxin, adrenodoxin) to redoxbasedmetabolisms in plastids, mitochondria and bacteria. The FNRvariants present in most prokaryotes (FPRs) can bephylogenetically classified into two subclasses represented by theAzotobacter vinelandii (subclass I) and the Escherichia coli(subclass II) FPR prototypes. Xanthomonas axonopodis pv. citri(Xac) is a Gram-negative, aerobic bacteria that possess a single fprgene with the characteristic features of subclass I bacterialreductases. We have expressed in E. coli and purified tohomogeneity the recombinant Xac FPR protein, rendering amonomeric product with an absorption spectrum characteristic offlavin-containing proteins. Then, we further characterized Xac FPRprotein by analyzing its kinetic behavior and interaction with thesubstrates NADPH, NADH, pea ferredoxin and E. coli flavodoxin.The accessibility of the prosthetic group FAD was also evaluated.Comparative analysis of the collected results with those reportedfor typical plastidic (i.e. pea) and bacterial (i.e. E. coli) FNRssuggest that Xac FPR resembles plastidic reductases regarding theinteraction with nucleotidic substrates and the prosthetic group, butdisplays kinetic parameters typical of bacterial flavoenzymes.