FLAVODOXIN REDUCTASES OF Acinetobacter. KINETIC CHARACTERIZACION AND RESPONSE TO REDOX STRESSORS

CORTEZ N; PALAVECINO NICOTRA MA; SARTORIO MG

Paraná, Entre Ríos

Congreso; 54th Annual Meeting Argentine Society for Biochemestry and Molecular Biology; 2018

Sociedad Argentina de Investigación Bioquímica y Biología Molecular

Ferredoxin/flavodoxin NADP(H)-reductases (FPRs) are monomeric flavoenzymes carrying non-covalently bound FAD as cofactor, present inmitochondria, plastids and bacteria. Bacterial FPRs are classified in two groups that differ in the C-terminus structure. They are involved inreductive activation of enzymes and repair of Fe-S clusters after oxidative damage. Although most bacteria contain one of the two forms, somespecies carry both of them. The extremophile UV-resistant Acinetobacter sp. Ver3 conserved both FPR1 and FPR2 and a single flavodoxin. Herewe report a biochemical characterization of the flavoenzymes and a study of their response to environmental factors as pro-oxidants or UVirradiation.Kinetic measurements under steady state conditions using flavodoxin as e- acceptor showed a faster electron transfer for FPR1compared to FPR2 (kcat1=1.3 s-1 vs. kcat2=0.5 s-1) with a higher Km for both flavodoxin (Km1=4.7 μM vs Km2=1.5 μM) and NADPH(Km1=85 μM vs Km2=34 μM).Challenge of Acinetobacter cells with superoxide propagators resulted in increased accumulation of FPR2 asrevealed by immunostaining with specific antibodies. However, when cells were exposed to UV radiation, only FPR1 levels augmented. Thesedata suggest that, although displaying similar catalytic efficiency, each FPR of Acinetobacter has a distinctive regulation mechanism in responseto different stressors and redox stimuli.