Kinetic control by limiting glutaredoxin amounts enables thiol oxidation in the reducing mitochondrial intermembrane space.
The mitochondrial intermembrane space (IMS) harbors an oxidizing machinery that drives import and folding of small cysteine-containing proteins without targeting signals. The main component of this pathway is the oxidoreductase Mia40, which introduces disulfides into its substrates. We recently showed that the IMS glutathione pool is maintained as reducing as that of the cytosol. It thus remained unclear how equilibration of protein disulfides with the IMS glutathione pool is prevented in order to allow oxidation-driven protein import. Here we demonstrate the presence of glutaredoxins in the IMS and show that limiting amounts of these glutaredoxins provide a kinetic barrier to prevent the thermodynamically feasible reduction of Mia40 substrates by the IMS glutathione pool. Moreover, they allow Mia40 to exist in a predominantly oxidized state. Consequently, overexpression of glutaredoxin 2 in the IMS results in a more reduced Mia40 redox state and a delay in oxidative folding and mitochondrial import of different Mia40 substrates. Our findings thus indicate that carefully balanced glutaredoxin amounts in the IMS ensure efficient oxidative folding in the reducing environment of this compartment.
Cellular Biochemistry, University of Kaiserslautern, 67663 Kaiserslautern, Germany.
Kerstin
K
Kojer
Cell Biology, University of Kaiserslautern, 67663 Kaiserslautern, Germany.
Valentina
V
Peleh
Cellular Biochemistry, University of Kaiserslautern, 67663 Kaiserslautern, Germany.
Gaetano
G
Calabrese
Cell Biology, University of Kaiserslautern, 67663 Kaiserslautern, Germany.
Johannes M
JM
Herrmann
Cellular Biochemistry, University of Kaiserslautern, 67663 Kaiserslautern, Germany jan.riemer@biologie.uni-kl.de.
Jan
J
Riemer
D003600:Cytosol / Q000378:metabolism; D054477:Glutaredoxins / Q000235:genetics / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism; D019803:Glutathione Disulfide / Q000378:metabolism; D015151:Immunoblotting; D007700:Kinetics; D045726:Metalloproteases / Q000235:genetics / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D033681:Mitochondrial Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D051336:Mitochondrial Membranes / Q000378:metabolism*; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010084:Oxidation-Reduction; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D013438:Sulfhydryl Compounds / Q000378:metabolism*
C491960:CCS1 protein, S cerevisiae; D054477:Glutaredoxins; C527885:Grx2 protein, S cerevisiae; C495320:MIA40 protein, S cerevisiae; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins; D018832:Molecular Chaperones; D029701:Saccharomyces cerevisiae Proteins; D013438:Sulfhydryl Compounds; C519195:ATP23 protein, S cerevisiae; D045726:Metalloproteases; D005978:Glutathione; D019803:Glutathione Disulfide