Rubrerythrin

Rubrerythrin (RBR) is a non-heme iron-containing metalloprotein involved in oxidative stress tolerance within anaerobic bacteria.^[1] It contains a di-iron active site, where peroxide is reduced into two water molecules, and a mono-iron rubredoxin-like domain thought to be involved in electron transfer.^[2] A majority of known RBR families are utilized as peroxide "scavengers" to defend organisms against oxidative stress.

Crystal structure of Rubrerythrin obtained from Pyrococcus furiosus using methods of X-ray diffraction..

Function

As a member of the Ferritin-like superfamily, RBRs primary function is iron storage and detoxification. Rubrerythrins utilize their di-iron centers to bind with reactive oxygen species such as Hydrogen Peroxide, further reducing them into water.

RBR reduction is theorized as a particularly important adaptation that occurred in response to the Great Oxygenation event, increasing defensive fitness of all cells exposed to relatively high levels of oxygen and similar byproducts.^[3]

Although primarily studied within anaerobic bacteria, RBRs have been discovered in multiple different types of cells including: Aerobic, Anaerobic, and Cyanobacteria.^[4]

Structure

Many formations of RBRs can be identified by four helical structures, chains alpha and beta containing 3 iron atoms. Both N and C-terminals of common RBRs are very similar to Rubredoxin containing amino acid residue sequences. Furthermore, both metalloproteins contain 5 histidine ligands located within the N-terminals of their peptide chains.^[5]

Mechanism

In a reduced state without exposure to reactive oxygen byproducts, Rubrerythrin contains two water molecules near its di-iron center. During and after exposure to peroxide, Rubrerythrin becomes oxidized, changing rotational conformations beginning around the peroxide binding site.^[6]