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Updated: Feb 7, 2026

Green Fluorescent Protein-based Expression Screening of Membrane Proteins in Escherichia coli
Published on: January 6, 2015
A protein-protein host-guest complex: Thermostable ferritin encapsulating positively supercharged green fluorescent
Katherine W Pulsipher1, Joshua A Bulos1, José A Villegas1
1Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, 19104.
Abstract:
We characterize the encapsulation of supercharged green fluorescent protein, GFP(+36), by thermophilic ferritin from Archaeoglobus fulgidus (AfFtn). The AfFtn-GFP(+36) assembly is rapid, nearly stoichiometric, and robust. Using a more stably assembled mutant AfFtn, we show that encapsulation can occur in the presence of mostly assembled cages, in addition to encapsulation starting from AfFtn individual subunits. Assembly and encapsulation do not occur with non-supercharged GFP or the alternately supercharged GFP(-30), highlighting the role of complementary electrostatic interactions between the cargo and AfFtn cage interior. We also present a method for verifying protein-protein encapsulation, using nickel nitrilotriacetic acid agarose resin. AfFtn-supercharged protein host-guest complexes could find applications in enzyme studies, protein separations, and in vivo protein stabilization and targeted delivery.
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