Functional characterization of mitochondrial peroxiredoxin (Prx1) in the redox physiology of Saccharomyces cerevisiae

Author(s)

Fernando Gomes

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB)
• Defense date: 2016-11-11

Examining board members

Luis Eduardo Soares Netto; Mário Henrique de Barros; Marilene Demasi; Gisele Monteiro de Souza

• Advisor: Luis Eduardo Soares Netto

Abstract

Peroxiredoxins (Prxs) are thiol-dependent peroxidases that catalyze the reduction of a wide variety of hydroperoxides. The Prxs catalytic activity is provided by the presence of a highly conserved catalytic cysteine residue whose oxidation by hydroperoxide generates sulfenic acid (Cys-SOH). Saccharomyces cerevsiae Prx1 is a mitochondrial enzyme that catalyzes the reduction of the H2O2 generated endogenously by mitochondria. The mechanism of reduction of Prx harboring Cys-SOH is a matter of debate, with glutaredoxin 2 (GRX2), thioredoxin 3 (Trx3), thioredoxin reductase 2 (Trr2), and ascorbate being proposed as possible reducers. To assess the functional role of Prx1 in maintaining the mitochondrial redox homeostasis, we investigated its mechanisms of import and processing, as well as those ones involved with its possible reducers, Trr2 and Trx3. Assays of solubility and mitochondrial sub-fractionation show that Prx1, Trr2 and Trx3 co-localize in the mitochondrial matrix compartment, being marginally associated with the inner mitochondrial membrane. In addition, Prx1 show dual localization, being also present in the mitochondrial intermembrane space, possibly in their soluble form. The import mechanism of Prx1 to the intermembrane space involves the release of protein\'s precursor within the lipid bilayer of the inner membrane due to a small, hydrophobic region located downstream the presequence. Imp2 subunit of the IMP protein complex then catalyzes the cleavage of the hydrophobic region of Prx1, releasing it to the mitochondrial intermembrane space. During its import into the matrix, Prx1 is sequentially cleaved by the mitochondrial processing-peptidase protease (MPP) and by octapeptidil aminopeptidase 1 (Oct1). Oct1 catalyzes the cleavage of eight amino acid residues from the N-terminal region of Prx1. This process increases stability of Prx1 inside the mitochondria, but does not interfere in its peroxidase activity in vitro. Interestingly, absence of Oct1 causes high instability of Trr2 and Trx3, although these proteins are not cleaved by this protease. Remarkably, the processing of Prxs by Oct1 seems to be a conserved process since yeast Oct1 is able to cleave the human mitochondrial peroxiredoxin Prx3 expressed in S. cerevisiae. Altogether, these results indicate the involvement of Oct1 in the processing of peroxiredoxins, representing a protein quality control system that regulates the homeostasis of Prxs and, possibly, mitochondrial redox processes (AU)

• FAPESP's process: 13/04240-6 - Functional characterization of mitochondrial peroxiredoxin (Prx1p) in the redox physiology of Saccharomyces cerevisiae
• Grantee: Fernando Gomes
• Support Opportunities: Scholarships in Brazil - Doctorate