Related Experiment Video

Updated: Sep 27, 2026

Green Fluorescent Protein-based Expression Screening of Membrane Proteins in Escherichia coli
08:46

Green Fluorescent Protein-based Expression Screening of Membrane Proteins in Escherichia coli

Published on: January 6, 2015

New membrane-associated and soluble peptide methionine sulfoxide reductases in Escherichia coli

Daniel Spector1, Frantzy Etienne, Nathan Brot

  • 1Center for Molecular Biology and Biotechnology, Florida Atlantic University, Boca Raton, FL 33431, USA.

Biochemical and Biophysical Research Communications
|February 27, 2003
PubMed

Insights

Researchers discovered novel enzymes in E. coli that reduce oxidized methionine residues in proteins. This finding helps explain how cells repair oxidative damage, particularly the R-epimer form of methionine sulfoxide.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Enzymology

Background:

  • Reactive oxygen species cause non-stereospecific oxidation of methionine residues in proteins.
  • Methionine sulfoxide reductases A (MsrA) and B (MsrB) enzymes reduce S and R forms of methionine sulfoxide, respectively.
  • Low MsrB activity in E. coli suggests alternative pathways for reducing R-methionine sulfoxide.

Purpose of the Study:

  • To identify novel enzymes in E. coli capable of reducing methionine sulfoxide.
  • To characterize the activity and substrate specificity of newly discovered methionine sulfoxide reductase activities.

Main Methods:

  • Utilized an Escherichia coli msrA/B double mutant.
  • Analyzed membrane vesicle and soluble extracts for peptide methionine sulfoxide reductase activity.
  • Assessed reduction of various methionine sulfoxide substrates, including N-acetylmethionine sulfoxide and D-ala-met(o)-enkephalin.
  • Determined cofactor requirements, identifying NADPH dependency.

Main Results:

  • A novel membrane-associated peptide methionine sulfoxide reductase activity was identified in E. coli msrA/B double mutants.
  • This membrane activity reduced both R and S forms of N-acetylmethionine sulfoxide, D-ala-met(o)-enkephalin, and methionine sulfoxide.
  • A new soluble Msr activity specifically reducing the S-epimer of methionine sulfoxide was also detected in soluble extracts.
  • The membrane-associated activity requires NADPH.

Conclusions:

  • The identified membrane-associated activity likely contributes to the reduction of R-methionine sulfoxide in E. coli.
  • These findings reveal additional enzymatic mechanisms for repairing oxidative damage to proteins in E. coli.
  • The study expands our understanding of methionine sulfoxide reductase systems in bacteria.

More Related Videos

Identification of Protein Complexes in Escherichia coli using Sequential Peptide Affinity Purification in Combination with Tandem Mass Spectrometry14:58

Identification of Protein Complexes in Escherichia coli using Sequential Peptide Affinity Purification in Combination with Tandem Mass Spectrometry

Published on: November 12, 2012

Production of Disulfide-stabilized Transmembrane Peptide Complexes for Structural Studies12:05

Production of Disulfide-stabilized Transmembrane Peptide Complexes for Structural Studies

Published on: March 6, 2013

Related Concept Videos

Protein Modifications in the RER01:26

Protein Modifications in the RER

Modification of secretory and transmembrane proteins entering the rough ER begins in the ER lumen. These modifications aid in protein folding and stabilize the acquired tertiary structure. Protein modifications in the rough ER co-occur at different stages of protein folding.
Broadly, these modifications can be categorized into four main categories — glycosylation, formation of disulfide bonds, assembly of protein subunits, and specific proteolytic cleavages like removal of signal sequences.
Insertion of Single-pass Transmembrane Proteins in the RER01:26

Insertion of Single-pass Transmembrane Proteins in the RER

Integral membrane proteins are proteins adhered to the lipid bilayer of a cell organelle or membrane. They can be of two types: transmembrane integral proteins that span the lipid bilayer and monotopic proteins that are attached to either side of the membrane but do not pass through it.
Integral transmembrane proteins possess transmembrane and extra membrane domains. The transmembrane domains are primarily made of 20-25 hydrophobic amino acids arranged in a helical secondary confirmation. These...
Export of Misfolded Proteins out of the ER01:32

Export of Misfolded Proteins out of the ER

After folding, the ER assesses the quality of secretory and membrane proteins. The correctly folded proteins are cleared by the calnexin cycle for transport to their final destination, while misfolded proteins are held back in the ER lumen. The ER chaperones attempt to unfold and refold the misfolded proteins but sometimes fail to achieve the correct native conformation. Such terminally misfolded proteins are then exported to the cytosol by ER-associated degradation or ERAD pathway for...
Chemotaxis in E. coli01:27

Chemotaxis in E. coli

Chemotaxis in Escherichia coli is a sensory-driven motility mechanism that enables bacteria to navigate chemical gradients, moving toward beneficial environments while avoiding harmful conditions. This process relies on a signal transduction system integrating external chemical cues with flagellar motor control.Chemoreceptors and Signal DetectionE. coli detects chemical gradients through methyl-accepting chemotaxis proteins (MCPs), which are membrane-bound chemoreceptors that sense attractants...
Protein Import into the Peroxisomes01:27

Protein Import into the Peroxisomes

Cells contain membrane-bound organelles called peroxisomes that oxidize organic molecules by transferring hydrogen atoms to oxygen, producing hydrogen peroxide. Peroxisomes enzymatically convert the released hydrogen peroxide into water and oxygen.
Peroxisomal Protein Import:
Peroxisomes lack the genetic machinery required to code for their own proteins. Hence, most peroxisomal membrane, lumenal and transmembrane proteins are synthesized in the cytoplasm or ER and transported to the peroxisome...
Stringent Response in E. coli01:23

Stringent Response in E. coli

Bacterial growth is closely tied to nutrient availability, with cells proliferating exponentially under favorable conditions and entering a stationary phase when resources become scarce. This transition is mediated by a regulatory mechanism known as the stringent response, which allows bacteria to adapt to nutrient deprivation by modulating gene expression and metabolic activity.During nutrient scarcity, intracellular amino acid levels decline. It results in the accumulation of uncharged tRNAs...