Biochemistry and function of methionine sulfoxide reductase

Research output: Chapter in Book/Report/Conference proceedingChapter

2 Citations (Scopus)


Reactive oxygen species (ROS) oxidize methionine to a mixture of methionine-S-sulfoxide and methionine-R-sulfoxide. Methionine is also oxidized by various flavin-containing monooxygenases in a partially or fully stereospecific manner. Methionine sulfoxide can be reduced by methionine sulfoxide reductase (Msr) proteins in four different families. Both free and protein-based forms of methionine-S-sulfoxide are reduced by MsrA, whereas protein-based methionine-R-sulfoxide is reduced by MsrB. Among the three known mammalian MsrBs, only MsrB1 is a selenoprotein, containing a selenocysteine residue in place of the catalytic cysteine. Free methionine-R-sulfoxide reductase (fRMsr) reduces methionine-R-sulfoxide in the free, but not protein-based state, and is found only in unicellular organisms, whereas MsrA and MsrB are present in organisms in all three kingdoms of life. MsrP reduces both methionine-S-sulfoxide and methionine-R-sulfoxide, particularly in membrane-embedded proteins, with assistance from MsrQ, which is involved in electron transport in the mitochondrial respiratory chain. MsrP cannot utilize thioredoxin as a reducing agent. Msrs are oxidoreductases that protect against the effects of oxidative stress by increasing oxidative stress resistance and repairing damaged proteins via cyclic methionine oxidation/reduction. In addition to its two main functions, MsrB1 reversibly regulates actin assembly in conjunction with Mical, making methionine oxidation similar to other reversible posttranslational modifications. This finding highlights a new era in the understanding of Msr function and should facilitate further studies of the physiological role of Msrs.

Original languageEnglish
Title of host publicationSelenium
Subtitle of host publicationIts Molecular Biology and Role in Human Health, Fourth Edition
PublisherSpringer International Publishing
Number of pages6
ISBN (Electronic)9783319412832
ISBN (Print)9783319412818
Publication statusPublished - 2016 Jan 1


  • Antioxidant
  • fRMsr
  • Methionine sulfoxide
  • Mical
  • MsrA
  • MsrB
  • MsrB1
  • MsrPQ

ASJC Scopus subject areas

  • Medicine(all)
  • Immunology and Microbiology(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)


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