• Open Access

Efficient N-Terminal Labeling of Proteins by Use of Sortase


  • We thank Dr. C. Neylon for providing an expression construct for sortase, Prof. K. Drickamer for providing a plasmid for expressing the ManBP variant, and Dr. T. Edwards and Dr. H. Jenkins for a sample of the pumilio protein. This work was supported by an EPSRC studentship for D.J.W. and also research grants EP/G043302/1, EP/I013083/1 and BB/G004145/1. W.B.T. thanks the Royal Society for a University Research Fellowship.


original image

“Sorting out” N-terminal labeling: The reversibility of transpeptidase reactions makes protein N-terminal labeling challenging. Depsipeptide substrates for sortase A release alcohol by-products, which are poor nucleophiles for the reverse reaction, during ligation. Proteins with an unhindered N-terminal glycine residue can be labeled efficiently with only a minimal excess of the labeling reagent (see scheme).