Thermostability of protein nanocages: the effect of natural extra peptide on the exterior surface

Protein nanocages have been used as functional bio-templates for the synthesis or organization of nanomaterials. However, the stability of these protein nanocages is nonideal, which limits their applications. Herein, we characterized the high thermal stability of plant ferritin, soybean seed H-2 ferritin (SSFH-2), the melting point (T-m) of which is 106 degrees C. We demonstrated that the hyperthermostability of SSFH-2 is derived from extra peptides (EP) located on its outer surface. Indeed, removal of the EP domains resulted in a dramatic decrease in T-m to 88 degrees C. Similar to EP-deleted plant ferritin, human H-chain ferritin (HuHF) has a T-m of 82 degrees C. Excitingly, the graft of the EP domain on the exterior surface of HuHF pronouncedly improved its T-m to 103 degrees C, which represents a simple, efficient approach to the construction of protein architectures with high stability. The remarkable stability of protein nanocages will greatly facilitate their application as robust biotemplates in the field of nanoscience.