Charge engineering controls cooperative assembly and loading in protein host-guest complexes.

This study explores the use of charge engineering to regulate the encapsulation of cargo proteins within self-assembling ferritin capsules. Guided by molecular dynamics simulations and computational protein design, the researchers engineered supercharged variants of green fluorescent protein (GFP) and demonstrated that the charge magnitude and distribution of the cargo dictate the efficiency of capsule assembly and loading. This work provides the first example of cooperative assembly between a cargo protein and a ferritin capsule, and establishes a strategy for generating stoichiometric 1:1 protein host-guest complexes, as confirmed by time-resolved fluorescence anisotropy. These findings offer a blueprint for designing ferritin host-guest complexes with enhanced homogeneity and functionality, with potential applications in areas such as drug delivery and nanomedicine.