Nanoscale elongating control of the self-assembled protein filament with the cysteine-introduced building blocks.

Self-assembly of artificially designed proteins is extremely desirable for nanomaterials. Here we show a novel strategy for the creation of self-assembling proteins, named "Nanolego." Nanolego consists of "structural elements" of a structurally stable symmetrical homo-oligomeric protein and "binding elements," which are multiple heterointeraction proteins with relatively weak affinity. We have established two key technologies for Nanolego, a stabilization method and a method for terminating the self-assembly process. The stabilization method is mediated by disulfide bonds between Cysteine-residues incorporated into the binding elements, and the termination method uses "capping Nanolegos," in which some of the binding elements in the Nanolego are absent for the self-assembled ends. With these technologies, we successfully constructed timing-controlled and size-regulated filament-shape complexes via Nanolego self-assembly. The Nanolego concept and these technologies should pave the way for regulated nanoarchitecture using designed proteins.