Skip to main content
. Author manuscript; available in PMC: 2014 May 1.
Published in final edited form as: J Am Chem Soc. 2013 Apr 17;135(17):6529–6540. doi: 10.1021/ja4005943

Figure 5.

Figure 5

Semi-synthesis of Double-Labeled Proteins with N-terminal Thioamides. Expressed C-terminal protein fragment: A) Using a plasmid encoding an N-terminal HisTag with a Factor Xa site; B) Using a plasmid encoding the truncated protein where N-terminal Met is removed by Met aminopeptidase. MeONH2•HCl used to cleave the thiazolidine which forms with intracellular aldehydes. (R = Me or CH2CO2H) Synthetic N-terminal thiopep-tide thioester: C) Synthesis on Cl-Trt resin and activation to form thioester with PyBOP, followed by deprotection with TFA; D) Synthesis on Rink amide resin with CbPGo masked thioester. The expressed protein fragment and synthetic thiopeptide are combined in the presence of thiophenol and the ligated, full-length protein isolated.