November 2009

Pass the Peroxide, Please

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biobit_roGFP

The roGFP2-Orp1(WT) fusion protein facilitates H2O­2-mediated oxidation in living cells, while the roGFP2-Orp1(CS) mutant cannot.

While hydrogen peroxide (H2O­2) can be quite damaging to proteins, it also can be an effective signaling agent if properly regulated; by oxidizing target thiol groups, H2O2 can produce reversible modifications that change the functional properties of proteins. But how do cells ensure that H2O­2 will oxidize redox-regulated target proteins in a specific and efficient manner? This study answers that question. Using redox-sensitive green fluorescent protein (roGFP) fusion proteins as a measurement tool (the redox-mediated formation of disulfide bridges produces fluorescence), the researchers found that the yeast peroxidase Orp1 could promote the oxidation of roGFP2 in a proximity-dependent manner, both in vitro and in mammalian cells. This “oxidant relay” was not restricted to Orp1, as the mammalian glutathione peroxidase Gpx4 also mediated roGFP2 oxidation. Together, these results suggest that certain enzymes in the glutathione peroxidase family may harbor a general capacity to facilitate thiol oxidation with closely associated proteins.

Proximity-based Protein Thiol Oxidation by H2O­2-scavenging Peroxidases

Marcus Gutscher, Mirko C. Sobotta, Guido H. Wabnitz, Seda Ballikaya, Andreas J. Meyer, Yvonne Samstag, and Tobias P. Dick

J. Biol. Chem., published online Sept. 15, 2009

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