The present invention relates to methods and compositions that provide an environment that promotes enhanced protein expressing and/or folding. More particularly, the present invention provides engineered thermostable ferritin assemblies comprising at least one modified ferritin subunit, wherein the least at least one modified ferritin subunit lacks an unstructured carboxy-terminal sequence that is present in a wildtype ferritin subunit and wherein the engineered assembly is stable at lower salt concentrations that a wildtype ferritin assembly. The invention is exemplified by a ferritin assembly derived from hyperthermophilic Archaeoglobus fulgidus. Also claimed are nucleic acids, compositions, kits and methods of encapsulating a polypeptide, delivering and administering the said engineered ferritin assembly to a subject.
