Structure and function of yeast glutaredoxin 2 depend on postranslational processing and are related to subcellular...

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Glutaredoxin 2 (Grx2) in Saccharomyces cerevisiae exhibits diverse subcellular localizations: cytosol, mitochondrial matrix, and outer membrane.
• These localizations arise from post-translational processing of a single Grx2 gene.
• Understanding the structural and functional implications of Grx2's varied cellular destinations is crucial.

Purpose of the Study:

• To investigate the correlation between Grx2's subcellular localization and its structural/functional differences.
• To elucidate the role of N-terminal modifications in Grx2 isoform function.
• To determine how targeting signal peptides influence Grx2's cellular fate and properties.

Main Methods:

• Mass spectrometry was used to determine the N-terminal sequence of mitochondrial matrix Grx2.
• Mitochondrial Processing Peptidase (MPP) cleavage sites were identified.
• Site-directed mutagenesis was employed to create Grx2 mutants targeted to specific compartments (cytosol, mitochondrial membrane, matrix).

Main Results:

• Mitochondrial matrix Grx2 has a basic tetrapeptide extension due to MPP cleavage, enhancing its GSSG reduction activity.
• Cytosolic Grx2 confers sensitivity to hydrogen peroxide (H2O2), similar to Grx2-deficient strains.
• Mitochondrial matrix Grx2 confers resistance to H2O2.
• Mutations in key basic residues of the targeting signal peptide significantly alter Grx2's cellular localization and function.

Conclusions:

• The N-terminal targeting signal peptide sequence dictates Grx2's subcellular localization and functional properties.
• Diversification of Grx2 structure and function is tightly regulated by its presequence.
• Mitochondrial localization of Grx2 is critical for cellular protection against oxidative stress.