Genetically Engineered Organization: Protein Template, Biological Recognition Sites, and Nanoparticles

Nanoparticles and their assemblies exhibit properties that can be used for a wide range of applications. However, creating multifunctional assemblies has remained challenging. Inspired by magnetotactic bacteria, genetically engineered single building blocks from magnetosome chains are used and complemented by additional components to form fluorescent assemblies of nanoparticles of varying types. This strategy is illustrated by the use of a protein from magnetotactic bacteria (MamK) known to form filaments in vivo and in vitro. A fusion protein of MamK and the fluorescent protein mCherry is recombinantly expressed and isolated using a hexahistidine tag that is subsequently used to bind functionalized gold nanoparticles to polymerized MamK_mCherry_His₆ filaments. The versatility of this modular approach is further exemplified by the concomitant addition of biological or synthetic magnetic nanoparticles functionalized with a nanobody directed against mCherry. The as-formed structures are fluorescent and can be actuated by an external magnetic field. This study shows again how nature's strategies can be applied for designing multifunctional materials.