Fig. 1

Formylglycine-generating enzyme (FGE) converts the Cys found within in its consensus sequence to an fGly residue. The FGE consensus sequence, CXPXR, where X is any residue except proline, is genetically encoded into a desired location within the target protein of interest, e.g., an antibody. Vectors encoding this “aldehyde-tagged” protein and the FGE enzyme are introduced into a cell; then, during protein production FGE cotranslationally modifies the Cys within the CXPXR sequence, removing the thiol group and replacing it with an aldehyde, resulting in an overall conversion from a Cys to a formylglycine (fGly) residue. The aldehyde group within the fGly serves as a chemical handle that can be used for downstream site-specific bioconjugation