Studies on the reducing systems for plant and animal thioredoxin-independent methionine sulfoxide reductases B

Biochem Biophys Res Commun. 2007 Sep 28;361(3):629-33. doi: 10.1016/j.bbrc.2007.07.072. Epub 2007 Jul 25.


Two distinct stereospecific methionine sulfoxide reductases (Msr), MsrA and MsrB reduce the oxidized methionine (Met), methionine sulfoxide [Met(O)], back to Met. In this report, we examined the reducing systems required for the activities of two chloroplastic MsrB enzymes (NtMsrB1 and NtMsrB2) from tobacco (Nicotiana tabacum). We found that NtMrsB1, but not NtMsrB2, could use dithiothreitol as an efficient hydrogen donor. In contrast Escherichia coli thioredoxin (Trx) could serve as a reducing agent for NtMsrB2, but not for NtMsrB1. Similar to previously reported human Trx-independent hMsrB2 and hMsrB3, NtMsrB1 could also use bovine liver thionein and selenocysteamine as reducing agents. Furthermore, the unique plant Trx-like protein CDSP32 was shown to reduce NtMsrB1, hMsrB2 and hMsrB3. All these tested Trx-independent MsrB enzymes lack an additional cysteine (resolving cysteine) that is capable of forming a disulfide bond on the enzyme during the catalytic reaction. Our results indicate that plant and animal MsrB enzymes lacking a resolving cysteine likely share a similar reaction mechanism.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Chloroplasts / enzymology
  • Cystamine / analogs & derivatives
  • Cystamine / chemistry
  • Cystamine / metabolism
  • Cysteine / chemistry
  • Cysteine / metabolism
  • Humans
  • Methionine Sulfoxide Reductases
  • Microfilament Proteins
  • Molecular Sequence Data
  • Organoselenium Compounds / chemistry
  • Organoselenium Compounds / metabolism
  • Oxidation-Reduction
  • Oxidoreductases / chemistry
  • Oxidoreductases / metabolism*
  • Oxidoreductases Acting on Sulfur Group Donors / chemistry
  • Oxidoreductases Acting on Sulfur Group Donors / metabolism
  • Plant Proteins / chemistry
  • Plant Proteins / metabolism*
  • Sequence Analysis, Protein
  • Substrate Specificity
  • Thioredoxins / metabolism*
  • Tobacco / enzymology
  • Transcription Factors / chemistry
  • Transcription Factors / metabolism*


  • Microfilament Proteins
  • Organoselenium Compounds
  • Plant Proteins
  • Transcription Factors
  • selenocystamine
  • Thioredoxins
  • Oxidoreductases
  • Oxidoreductases Acting on Sulfur Group Donors
  • MSRB2 protein, human
  • Methionine Sulfoxide Reductases
  • methionine sulfoxide reductase
  • MSRB3 protein, human
  • Cysteine
  • Cystamine