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Structure and mechanism of peptide methionine sulfoxide reductase, an "anti-oxidation" enzyme
W T Lowther1, N Brot, H Weissbach
1Institute of Molecular Biology, Howard Hughes Medical Institute and Department of Physics, University of Oregon, Eugene, Oregon 97403, USA.
Abstract:
Peptide methionine sulfoxide reductase (MsrA) reverses oxidative damage to both free methionine and methionine within proteins. As such, it helps protect the host organism against stochastic damage that can contribute to cell death. The structure of bovine MsrA has been determined in two different modifications, both of which provide different insights into the biology of the protein. There are three cysteine residues located in the vicinity of the active site. Conformational changes in a glycine-rich C-terminal tail appear to allow all three thiols to come together and to participate in catalysis. The structures support a unique, thiol-disulfide exchange mechanism that relies upon an essential cysteine as a nucleophile and additional conserved residues that interact with the oxygen atom of the sulfoxide moiety.
Insights
Peptide methionine sulfoxide reductase (MsrA) repairs oxidative damage to proteins, protecting cells from death. Structural studies reveal its unique catalytic mechanism involving cysteine residues and conformational changes.
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Biology
Background:
- Oxidative stress causes damage to proteins, including methionine oxidation.
- Peptide methionine sulfoxide reductase (MsrA) is a key enzyme that repairs methionine oxidation.
- Cellular protection against oxidative damage is crucial for survival.
Purpose of the Study:
- To elucidate the structural basis of bovine MsrA function.
- To understand the catalytic mechanism of MsrA in repairing protein oxidation.
- To investigate the role of cysteine residues and conformational changes in MsrA activity.
Main Methods:
- X-ray crystallography was used to determine the structure of bovine MsrA.
- Analysis of two different MsrA modifications provided insights into its conformational flexibility.
- Biochemical assays were employed to study the catalytic mechanism.
Main Results:
- The structures revealed three cysteine residues near the active site.
- Conformational changes in a glycine-rich C-terminal tail facilitate the convergence of thiols for catalysis.
- A unique thiol-disulfide exchange mechanism involving essential cysteines and conserved residues was supported.
Conclusions:
- Bovine MsrA employs a distinct catalytic mechanism to reverse methionine oxidation.
- Structural insights highlight the importance of conformational flexibility and specific residues in MsrA's protective function.
- Understanding MsrA's mechanism can inform strategies against oxidative stress-related damage.