Functional and evolutionary characterization of Ohr proteins in eukaryotes reveals many active homologs among pathogenic fungi

Autor(es)

Meireles, A. ; Domingos, R. M. ; Gaiarsa, J. W. ; Ragnoni, E. G. ; Bannitz-Fernandes, R. ; da Silva Neto, J. F. ; de Souza, R. F. ; Netto, L. E. S.

• Tipo de documento: Artigo Científico
• Fonte: REDOX BIOLOGY; v. 12, p. 600-609, AUG 2017.
• Citações Web of Science: 5

Resumo

Ohr and OsmC proteins comprise two subfamilies within a large group of proteins that display Cys-based, thiol dependent peroxidase activity. These proteins were previously thought to be restricted to prokaryotes, but we show here, using iterated sequence searches, that Ohr/OsmC homologs are also present in 217 species of eukaryotes with a massive presence in Fungi (186 species). Many of these eukaryotic Ohr proteins possess an N-terminal extension that is predicted to target them to mitochondria. We obtained recombinant proteins for four eukaryotic members of the Ohr/OsmC family and three of them displayed lipoyl peroxidase activity. Further functional and biochemical characterization of the Ohr homologs from the ascomycete fungus Mycosphaerella fijiensis Mf\_1 (MfOhr), the causative agent of Black Sigatoka disease in banana plants, was pursued. Similarly to what has been observed for the bacterial proteins, we found that: (i) the peroxidase activity of MfOhr was supported by DTT or dihydrolipoamide (dithiols), but not by beta-mercaptoethanol or GSH (monothiols), even in large excess; (ii) MfOhr displayed preference for organic hydroperoxides (CuOOH and tBOOH) over hydrogen peroxide; (iii) MfOhr presented extraordinary reactivity towards linoleic acid hydroperoxides (k= 3.18 (+/- 2.13) x10(8) M-1 s(-1)). Both Cys(87) and Cys(154) were essential to the peroxidase activity, since single mutants for each Cys residue presented no activity and no formation of intramolecular disulfide bond upon treatment with hydroperoxides. The pK(a) value of the Cys(p) residue was determined as 5.7 +/- 0.1 by a monobromobimane alkylation method. Therefore, eukaryotic Ohr peroxidases share several biochemical features with prokaryotic orthologues and are preferentially located in mitochondria. (AU)

• Processo FAPESP: 12/21722-1 - Caracterização estrutural e bioquímica de proteínas da família Ohr/OsmC: ênfase para a caracterização de uma proteína de Francisella tularensis envolvida em patogenicidade
• Beneficiário: Diogo de Abreu Meireles
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 13/07937-8 - Redoxoma
• Beneficiário: Ohara Augusto
• Modalidade de apoio: Auxílio à Pesquisa - Centros de Pesquisa, Inovação e Difusão - CEPIDs