New membrane-associated and soluble peptide methionine sulfoxide reductases in Escherichia coli.
It is known that reactive oxygen species can oxidize methionine residues in proteins in a non-stereospecific manner, and cells have mechanisms to reverse this damage. MsrA and MsrB are members of the methionine sulfoxide family of enzymes that specifically reduce the S and R forms, respectively, of methionine sulfoxide in proteins. However, in Escherichia coli the level of MsrB activity is very low which suggested that there may be other enzymes capable of reducing the R epimer of methionine sulfoxide in proteins. Employing a msrA/B double mutant, a new peptide methionine sulfoxide reductase activity has been found associated with membrane vesicles from E. coli. Both the R and S forms of N-acetylmethionine sulfoxide, D-ala-met(o)-enkephalin and methionine sulfoxide, are reduced by this membrane associated activity. The reaction requires NADPH and may explain, in part, how the R form of methionine sulfoxide in proteins is reduced in E. coli. In addition, a new soluble Msr activity was also detected in the soluble extracts of the double mutant that specifically reduces the S epimer of met(o) in proteins.
Spector
Daniel
D
Center for Molecular Biology and Biotechnology, Florida Atlantic University, Boca Raton, FL 33431, USA.
Etienne
Frantzy
F
Brot
Nathan
N
Weissbach
Herbert
H
D002462:Cell Membrane / Q000201:enzymology; D004926:Escherichia coli / Q000201:enzymology*; D051150:Methionine Sulfoxide Reductases; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D012995:Solubility
D010455:Peptides; D010088:Oxidoreductases; D051150:Methionine Sulfoxide Reductases; C027219:methionine sulfoxide reductase