Post‐Assembly Modification of Protein Cages by Ubc9‐Mediated Lysine Acylation

Although viruses have been successfully repurposed as vaccines, antibiotics, and anticancer therapeutics, they also raise concerns regarding genome integration and immunogenicity. Virus‐like particles and non‐viral protein cages represent a potentially safer alternative but often lack desired functionality. Here, we investigated the utility of a new enzymatic bioconjugation method, called lysine acylation using conjugating enzymes (LACE), to chemoenzymatically modify protein cages. We equipped two structurally distinct protein capsules with a LACE‐reactive peptide tag and demonstrated their modification with diverse ligands. This modular approach combines the advantages of chemical conjugation and genetic fusion and allows for site‐specific modification with recombinant proteins as well as synthetic peptides with facile control of the extent of labeling. This strategy has the potential to fine‐tune protein containers of different shape and size by providing them with new properties that go beyond their biologically native functions.