Redox proteins and antioxidant response

Summary

The use of oxygen during respiration by aerobic cells turned into an evolutive advantage, due to the high energy yield of its reduction to water. However, the unavoidable by-products of oxygen partial reduction are highly toxic and react with all biomolecules. They are commonly referred to as reactive oxygen species (ROS) as the peroxydes, the superoxide and the hydroxyl radical.

Metabolic pathways involving electron exchange -as photosynthesis and respiration- can produce harmful oxidants through side- reactions. Along evolution, aerobic organisms developed several antioxidant defense mechanisms. These include protective systems that avoid oxidant damage, as detoxifying enzymes and scavengers, and also reparing systems, which operates after the oxidative damage has occured.

The current work of our group concern some of the redox enzymes involved in the biological antioxidant response of diverse prokaryotic models.

Research Lines

Redox proteins and antioxidant response.

The use of oxygen during respiration by aerobic cells turned into an evolutive advantage, due to the high energy yield of its reduction to water. However, the unavoidable by-products of oxygen partial reduction are highly toxic and react with all biomolecules. They are commonly referred to as reactive oxygen species (ROS) as the peroxydes, the superoxide and the hydroxyl radical. Aerobic organisms evolved diverse antioxidant mechanisms, including scavenging enzymes that destroy ROS, and repairing enzymes involved in restore normal cell function after oxidative injury took place. The current work of our group concerns some of the redox enzymes involved in the biological antioxidant response of diverse prokaryotic models, including the photosynthetic bacterium Rhodobacter capsulatus and extremophile bacterial isolates from argentine andean lakes. We focus specially on redox enzymes involved in scavenging ROS and in reparation of oxidative damage. Interested in the activity, structure and regulation of metallo-superoxide dismutase, we could describe how Rhodobacter displayed its ability to exploit natural availability of iron and manganese to produce different holoenzymes adapted to specific redox conditions during aerobic or photosynthetic metabolism. The structural features of an oxidant responsive flavodoxin:NADP(H) reductase probably involved in the reparation of damaged Fe-S clusters and in nitrogen fixation are studied as well. The identification of its native protein substrates (ferredoxins and flavodoxins) will enlighten its actual biological function.

Involvement of antioxidant proteins in adaptative mechanisms of extremophile bacteria

Andean wetlands are characterized by extreme environmental conditions such as high UV radiation, elevated salinity and arsenic content. A research line of our group concerns the study of the interaction between antioxidant mechanisms and the tolerance to the extreme environment
present in bacterial isolates collected from High Andean wetlands located 4400m above sea level. We observed that a particularly high catalase activity displayed by Acinetobacter Andean isolates could play an important role in tolerance towards high UV radiation and extreme environmental conditions.

Selected Publications

  • Di Capua, C., Bortolotti, A., Farías, M. E., Cortez, N. (2011). UV-resistant Acinetobacter sp. isolates from Andean wetlands display high catalase activity. FEMS Microbiol. Lett. 317, 181-189
  • Dumit, V. I., Cortez, N., Ullmann, G. M. (2011). Distinguishing two groups of flavin reductases by analyzing the protonation state of an active site carboxylic acid. Proteins 79, 2076-2085.
  • Dumit, V. I., Essigke, T., Cortez, N., Ullmann, G. M. (2010). Mechanistic Insights into Ferredoxin–NADP(H) Reductase Catalysis Involving the Conserved Glutamate in the Active Site. J. Mol. Biol. 397, 814-825.
  • Bortolotti, A., Pérez-Dorado, I., Goñi, G., Medina, M., Hermoso, J., Carrillo, N., Cortez, N. (2009) Coenzyme binding and hydride transfer in Rhodobacter capsulatus ferredoxin/flavodoxin NADP(H) oxidoreductase.
  • Tabares, L. C., Cortez, N., Un, S. (2007). Role of Tyrosine-34 in the Anion Binding Equilibria in Manganese(II) Superoxide Dismutases. Biochemistry 46, pp 9320–9327.
  • Tabares, L. C., Bittel, C., Carrillo, N., Bortolotti, A., Cortez, N. (2003). The single superoxide dismutase of Rhodobacter capsulatus is a cambialistic Mn-containing enzyme. J. Bacteriol. 185, 3223-3227.

Collaborators

  • María Eugenia Farías, PROIMI (CCT-Tucumán, CONICET).
  • Héctor Álvarez (Univ. Nac. de la Patagonia San Juan Bosco, Cdro. Rivadavia).
  • Milagros Medina (Universidad de Zaragoza, BIFI, España).
  • Juan Hermoso (Inst. Rocasolano, Madrid, España).
  • Matthias Ullmann (Bayreuth Universität, Alemania).
  • Werner Mäntele (Inst. Biophysik, Frankfurt Universität, Alemania)

Grants

  • CONICET

Director

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Cortez, Néstor
Core Faculty
Email: cortez@ibr-conicet.gov.ar
Phone: +54 341 4350596/4350661
Office Extension: 140
Laboratory Extension: 110

Doctoral fellows

  • Mariana Sartorio
  • Marcelo Palavecino Nicotra
  • Steimbruch Bruno

Undergraduate Students

  • Santiago Chaillou

Imágenes

La movilidad de la extensión C‐terminal presente en las formas bacterianas de la flavodoxina reductasa FPR, obtenida luego de cristalografía de los complejos enzima:nucleótido permitió visualizar su función en la modulación de la interacción de la proteína con su sustrato y de su actividad (Bortolotti et al., 2010).