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Oxidative stress

Rubrerythrins are a family of proteins which contain two domains: a N-terminal erythrin-like domain containing a four helix bundle with a diiron site, and a C-terminal rubredoxin-like domain containing a FeCys4 center. These proteins were first isolated from anaerobic and microaerobic organisms, e.g., Desulfovibrio vulgaris, Clostridium and Porphyromonas species .They have also been isolated from archaea, e.g., Sulfolobus tokodaii, and eukarya, e.g., Trichomonas vaginalis. The function of these proteins is, as yet, not fully established, and different activities have been reported for them, such as ferroxidase, superoxide dismutase, pyrophosphatase and NADH peroxidase activity, the latter being the most consensual. Rubrerythrins have also been found to complement catalase null strains, and rubrerythrin deletion mutants are known to be more sensitive to oxygen and hydrogen peroxide.
I have been studying the desulforubrerythrin from Campylobacter jejuni, which is a rubrerythrin type of protein, with a desulforredoxin domain with a FeCys4 center on the N-terminal.


Superoxide reductase
Superoxide reductases are proteins involved on the reduction of the superoxide anion (O2.-) generating H2O2. These enzymes are quite distinct from the superoxide dismutases (SOD) since these ones are responsible for the dismutation of superoxide anion, while the SORs are only able to perform the reductive step. These proteins have been classified according to their iron-content in two families: 1Fe-SORs, initially named neelaredoxin due to their blue color, and the 2Fe-SORs, known as desulfoferrodoxins, that contains an extra iron atom coordinated by four cysteine-sulfurs in a distorted tetrahedral geometry [Fe(Cys)4]. Structurally these two families are similar, with a common domain harbouring the catalytic center. This center, where the reduction of superoxide occurs, is conserved and is a pentacoordinated iron ion with four equatorial histidine-imidazoles and one axial cysteine-sulfur in a square pyramidal geometry. These proteins are quite widespread among the three domains of life.
I am currently interested on the structural determination and characterization of different proteins belonging to this family.


Flavodiiron proteins
Flavodiiron proteins have been described as part of the response mechanism against both nitrosative and oxidative stresses. This type of proteins are also widespread in anaerobic and facultative microrganisms, from the three life domains. Structurally these proteins are minimally composed by two domains, a metallo β-lactamase like domain, at the N-terminal, that contains a diiron site where reduction of oxygen or nitric oxide occurs, followed by a flavodoxin-like domain that contains an FMN group. More complex arrangements have been described, involving mainly extra domains at the C-terminus (e.g., rubredoxin or flavin reductases-like domains).
I am currently interested on the structural determination and characterization of different proteins belonging to this family.


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