Taylor, M. T. et al. Nature 562, 563–568 (2018).

The chemical manipulation of specific amino acids in native proteins is a useful approach for probing protein structure and function. Chemistries exist to modify cysteine, lysine and tyrosine residues, but expansion of this toolbox to other amino acids would be a welcome development. Methionine in particular represents a useful target for modification, because it is rare and its function is mainly to protect against oxidative stress, which means that its modification is unlikely to affect protein function. Taylor et al. report a bioconjugation method for methionine, based on the use of a hypervalent iodine reagent that targets the S-Me group. The reaction is selective, efficient and fast, and can be carried out in a one-pot operation. The researchers applied it to modify several native peptides and proteins, and show that the chemistry is compatible with methods for labeling other residues.