Intermediate Tyrosyl Radical and Amyloid Structure in Peroxide-Activated Cytoglobin.

Juliana C Ferreira,Otaciro R Nascimento,Thyago H S Cardoso,Aryane Tofanello,Vitor Oliveira,Tatiana Prieto,Felipe S Pessoto,Marcelo F Marcondes,Iseli L Nantes,Erica G A Miranda,Marcelo Y Icimoto,David Jourd'Heuil

doi:10.1371/journal.pone.0136554

Juliana C Ferreira, Otaciro R Nascimento + Show 10 more

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https://doi.org/10.1371/journal.pone.0136554

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Abstract

We characterized the peroxidase mechanism of recombinant rat brain cytoglobin (Cygb) challenged by hydrogen peroxide, tert-butylhydroperoxide and by cumene hydroperoxide. The peroxidase mechanism of Cygb is similar to that of myoglobin. Cygb challenged by hydrogen peroxide is converted to a Fe4+ oxoferryl π cation, which is converted to Fe4+ oxoferryl and tyrosyl radical detected by direct continuous wave-electron paramagnetic resonance and by 3,5-dibromo-4-nitrosobenzene sulfonate spin trapping. When organic peroxides are used as substrates at initial reaction times, and given an excess of peroxide present, the EPR signals of the corresponding peroxyl radicals precede those of the direct tyrosyl radical. This result is consistent with the use of peroxide as a reducing agent for the recycling of Cygb high-valence species. Furthermore, we found that the Cygb oxidation by peroxides leads to the formation of amyloid fibrils. This result suggests that Cygb possibly participates in the development of degenerative diseases; our findings also support the possible biological role of Cygb related to peroxidase activity.

Highlights

Globins are heme proteins that are widely found in bacteria, fungi, plants and animals
We have demonstrated that Cygb possesses peroxidase activity against hydrogen peroxide and organic peroxides involving a mechanism similar to that described for myoglobin
The direct detection of organic peroxyl radicals in the early times of the reaction suggests that organic peroxides can be used as recycling agents for Cygb high-valence species

Summary

Introduction

Globins are heme proteins that are widely found in bacteria, fungi, plants and animals. For Ngb and Cygb, which were discovered more recently, their biological function is an ongoing topic of discussion. A variety of biological roles have been assigned to Cygb, the subject of the present study. These roles include participation in oxygen supply for cells [5,11,12], acting as a reservoir and sensor of molecular oxygen for tissues [13,14,15,16], participating in the metabolism of NO [17,18,19,20,21], stimulating collagen synthesis in processes of tissue regeneration [22], impairing

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