Fabrication of uniform layer-by-layer assemblies with complementary protein cage nanobuilding blocks via simple His-tag/metal recognition

Abstract

A capsid-forming enzyme, lumazine synthase isolated from hyperthermophile Aquifex aeolicus (AaLS), is prepared and utilized as a template for constructing nanobuilding blocks to fabricate uniform layer-by-layer (LbL) assemblies. Two functionally complementary AaLS protein cage nanoparticles (PCNs) are generated either by genetically introducing His-tags on the surface of wild-type AaLS PCNs or by chemically attaching metal chelates (Ni–NTA moiety) to the surface of cysteine-bearing AaLS PCNs individually. The multivalent displays of His-tags (AaLS-His₆ PCN) and Ni–NTA ligands (AaLS-NTA–Ni PCN) on the surface of each complementary AaLS PCN are successfully demonstrated by mass spectrometric and surface plasmon resonance analyses. By using these two complementary AaLS PCNs, uniform LbL assemblies are constructed via simple recognition between His-tags and metal chelates without the aid of additional binding mediators. This approach illustrates the potential of fabricating uniform nanostructures using protein-based hybrid functional nanobuilding blocks.