Protein Needles as Molecular Templates for Artificial Metalloenzymes

Abstract

Construction of artificial metalloenzymes based on protein assemblies is a promising strategy for the development of new catalysts, because the three-dimensional nanostructures of proteins with defined individual sizes can be used as molecular platforms that allow the arrangement of catalytic active centers on their surfaces. Protein needles/tubes/fibers are suitable for supporting various functional molecules, including metal complexes, synthetic molecules, metal nanoparticles, and enzymes with high densities and precise locations. Compared with bulk systems, the protein tube- and fiber-based materials have higher activities for catalytic reactions and electron transfer, as well as enhanced functions when used in electronic devices. The natural and synthetic protein tubes and fibers are constructed by self-assembly of monomer proteins or peptides. For more precise designs of arrangements of metal complexes, we have developed a new conceptual framework, based on the isolation of a robust needle structure from the cell-puncturing domains of a bacteriophage. The artificial protein needle shows great promise for use in creating efficient catalytic systems by providing the means to arrange the locations of various metal complexes on the protein surface. In this account, we discuss the recent development of protein needle-based metalloenzymes, and the future developments we are anticipating in this field.