Metabolic labeling, proteins

Wu, Y., and Craig, A. (2006). Comparative proteomic analysis of metabolically labelled proteins from Plasmodium falciparum isolates with different adhesion properties. Malar. ]. 5,67. 

The use of the in vivo labeling methods described above is limited by the fact that the sample must be grown in the presence of the labeling isotopes. In many cases, it is not feasible to perform in vivo metabolic labeling. For example, for human clinical samples it is not possible to perform in vivo labeling and yet it is highly desirable to obtain accurate quantitative information on protein expression levels within these samples. Therefore, robust methods are needed for quantitation of protein levels in the absence of in vivo labeling with isotopes. 

Analytical tools have been developed in order to identify carbohydrate structures as well as carbohydrate-binding proteins and to understand their underlying structure-function relationships of protein-carbohydrate and carbohydrate-carbohydrate interactions lectin arrays [16], glycan microarrays [17, 18], glyco-nanoparticles [19], frontal affinity chromatography [20] and carbohydrate tools for metabolic labeling [21]. 

Sakurai, N., Moriya, K., Suzuki, T., Sofiiku, K, Motiki, H., Nishimura, O., and Utsmni, T. (2007) Detection of co- and post-translational protein N-myristoylation by metabolic labeling in an insect cell-free protein synthesis system. Anal. Biochem. 362, 236-244. 

Analysis of the primary protein structure of the human 5-HT1B receptor reveals a putative site for palmitoylation, i.e., a cysteine residue located in the short carboxyl tail of the receptor (141). A recombinant c-myc epitope-tagged 5-HT1B receptor was expressed in Sf9 insect cells and palmitoylation of the receptor was demonstrated by metabolic labeling of the cells with [3H]palmitic acid. 

Metabolic labeling generally exploits the incorporation of isotopic amino acids during the process of cellular metabolism, which includes protein synthesis. Cellular groups are grown in media containing different isotopic amino acids. After cell harvesting, the protein concentrations are equalised and pooled before MS as well as MS/MS analysis takes place. 

Metabolic labeling is an in situ method which employs or isotope-encoded ( C or H) amino acids. Organisms are grown in controlled media under defined conditions in order to ensure translation of mRNA entities to uniformly isotopically encoded proteins. Consequently, the approach is generally restricted to cell culture systems and is not applicable to quantitative MS analysis of proteins derived from... 

Inverse 15N-metabolic labeling/ mass spectrometry for comparative proteomics and rapid identification of protein markers/targets. Rapid Commun. Mass Spectrom. 16, 1389-1397. 

Figure 13.7 Schematic representation of quantification using metabolic labeling of relative abundances of proteins from two cell populations.

---