Template-Directed Assembly of a de Novo Designed Protein

Many naturally occurring biomaterials are composed of laminated structures in which layers of β-sheet proteins alternate with layers of inorganic mineral. These ordered laminates often have structural and mechanical properties that differ significantly from those of nonbiological materials. An important step in the construction of novel biomaterials is the creation of composites wherein a de novo designed protein assembles into an ordered structure. To achieve this goal, we layered a de novo protein onto the surface of highly ordered pyrolytic graphite (HOPG). The protein was derived from a combinatorial library of novel sequences designed to fold into amphiphilic β-sheet structures. Atomic force microscopy reveals that the protein assembles on the HOPG surface into ordered fibers aligned in three orientations at 120° to each other. The symmetry and extent of the ordered regions indicate that the hexagonal lattice underlying the graphite surface templates assembly of millions of protein molecules into a highly ordered structure.