An engineered closed-shell, two-component, 480-subunit nucleocapsid

Self-assembling protein cages are valuable nanoscale containers for biotechnology and medical applications. Two-component systems are especially attractive due to their potential for functional complexity. In this study, we demonstrate that the subunits of the 240-subunit nucleocapsid NC-4, which was previously evolved to package and protect its encoding mRNA, can be split into two fragments without disrupting cage assembly or structure, generating a two-component, 480-subunit capsid. This modification introduces additional termini on the cage's exterior surface, creating opportunities for functionalization. We exploited these new sites by genetically appending peptide and protein tags to the exterior surface of split NC-4 (spNC-4), enabling site-specific glycosylation via posttranslational modification and cell-specific delivery by targeted antibody recruitment. Our findings broaden the utility of the NC-4 nucleocapsid. By extension, splitting related protein compartments that bind diverse cargoes could offer a robust platform for biotechnological applications requiring simultaneous encapsulation and customizable surface modification.