Korea Basic Science Institute

Kun Cho

Jong Shin Yoo

Jin Young Kim

Yeong Hee Ahn

Jae Yong Lee

The present invention relates to a method for phosphorylation site-specific labeling of phosphoproteome with a site-specific tagging reagent and analyzing of the resulting labeled one, more especially, a method for in-situ tagging of phosphorylation sites of phosphoproteins retained in polymeric gel with a nucleophilic tagging reagent. It also relates a method for generating new proteolytic cleavable sites at formerly phosphorylation sites by a proper choice of a nucleophilic tagging reagent. It also relates to a method for phosphopeptides analysis and phosphorylation site identification by in-gel digestion of the previously in-gel tagged proteins and subsequent mass analysis of the resulting peptides. The invention provides in-gel chemical tagging method for phosphoaminoacid residue of phosphoproteins retained in polymeric gel matrix. Phosphoprotein can be immobilized into gel matrix by a variety of methods such as gel electrophoresis. The immobilized phosphoproteins are retained in gel matrix during tagging reaction to phosphorylated aminoacid residue of phosphoproteins, and the resulting tagged proteins are also retained in gel matrix till following purification steps like washing of the tagging reagents are accomplished. The tagged proteins is digested by protease, and the resulting digested peptides is released from gel into solution and applied for peptide mass analysis. 

In-gel tagging and in-gel digestion for phosphoproteins analysis and phosphorylation site identification

Disclosed is a method of analyzing mass of the phosphoproteins or phosphopeptides and of analyzing phosphorylated positions at a phosphoprotein or phosphopeptide, comprising the steps of: 1) dephosphorylating at least one Ser and/or Thr residue of the phosphoprotein or phosphopeptide; 2) tagging the dephosphorylated amino acid residues with a tag having a R-L-G moiety wherein R is a nucleophilic functional group that selectively bind with dephosphorylated amino acid residues, G is selected from the group consisting of guanidine moiety or protected guanidine moiety such as a mono-N-protected guanidino group, a di-N,N'-protected guanidino group and an N&#x2032;-protected guanidino group, and L is a linker linking the R and the G; and 3) subjecting the tagged proteins or peptides to mass spectrometry. The method is capable of precisely analyzing mass of phosphoproteins of trace amounts as well as positions of phosphoryated amino acids.

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Daejeon-Shi, South Korea

Kun Cho