This C-terminal Sortagging peptide acts as an (oligo)glycine nucleophile in the final steps of a sortagging protein labelling reaction. This reaction results in the [Cys(AF680)]- fluorescent moiety being attached to the C-terminus of the target protein or peptide.

A substrate peptide containing the LPXTG motif is recognised and cleaved by the enzyme Sortase A (SrtA) from Staphylococcus aureus. The catalytic cysteine residue in the active site of SrtA serves as a nucleophile to cleave the peptide bond between threonine and glycine of the substrate peptide. Cleavage results in the formation of a thioacyl intermediate between the substrate peptide and SrtA. This intermediate is then resolved by the N-terminus of this (oligo)glycine nucleophile peptide, resulting in the creation of a new peptide bond that links the substrate peptide to this peptide and its fluorescent dye.  This method of protein labelling is known as sortagging.

C-Terminal Sortagging-[Cys(AF680)] contains the AF680 fluorescent dye; AF680 is a bright green dye with excitation at 633 nm, well suited for flow cytometry and imagery. AF680 is particularly photostable, allowing better detection of low abundance conjugates.  C-Terminal Sortagging-[Cys(AF680)] acid is provided here. However, the amide version is also available here.