Targeted proteomics is a mass spectrometry-based method for the identification and quantification of a pre-defined set of proteins with high precision.
Xian et al. (2016) showed that a cell-free expression system allows the synthesis of isotope-labeled peptides. Fusing peptides to a quantitative tag enables magnetic-bead-based enrichment. Furthermore, the fused peptide tag enables global quantification via multiple reaction monitoring mass spectrometry, useful for targeted proteomics.
The research group adopted an Escherichia coli-based cell-free protein expression system using recombinant elements for the synthesis of isotope-labeled peptides fused to a Strep-tag. Strep-Tactin affinity enrichment enables the quantification of labeled peptides with good yields. To quantify peptides, trypsin digestion releases the Strep-tag, enabling multiple reaction monitoring mass spectrometry.
References
Isotope Labeling Peptide | Stable Heavy Isotope Peptide
What-is-an-isotope?
Xian F, Zi J, Wang Q, Lou X, Sun H, Lin L, Hou G, Rao W, Yin C, Wu L, Li S, Liu S. Peptide Biosynthesis with Stable Isotope Labeling from a Cell-free Expression System for Targeted Proteomics with Absolute Quantification. Mol Cell Proteomics. 2016 Aug;15(8):2819-28. [PMC]
Yeliseev A, Zoubak L, Schmidt TGM. Application of Strep-Tactin XT for affinity purification of Twin-Strep-tagged CB2, a G protein-coupled cannabinoid receptor. Protein Expr Purif. 2017 Mar;131:109-118. [PMC]
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