Design, synthesis, and characterization of protein origami based on self-assembly of a brick and staple artificial protein pair

Significance

Spontaneous building of bio-inspired organization with both accurate morphologies and well-defined functions is still highly challenging. We illustrate a versatile approach to control assemblies of complementary “staple” and “brick” proteins into supramolecular accurate architectures by characterizing de novo superhelixcrystals. For this purpose, we exploit the highly selective binding surfaces of repeat proteins to generate robust close contacts. We design the brick protein with a semi-lock washer shape by splitting and appending the sequence of the partner protein to its terminal modules. Equimolar mixture results in sequential growth generating long tubular superhelices. This strategy paves the way to chimeric proteins able to organize functions on designed structures by origami processes.

Abstract

A versatile strategy to create an inducible protein assembly with predefined geometry is demonstrated. The assembly is triggered by a binding protein that staples two identical protein bricks together in a predictable spatial conformation. The brick and staple proteins are designed for mutual directional affinity and engineered by directed evolution from a synthetic modular repeat protein library. As a proof of concept, this article reports on the spontaneous, extremely fast and quantitative self-assembly of two designed alpha-repeat (αRep) brick and staple proteins into macroscopic tubular superhelices at room temperature. Small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM with staining agent and cryoTEM) elucidate the resulting superhelical arrangement that precisely matches the a priori intended 3D assembly. The highly ordered, macroscopic biomolecular construction sustains temperatures as high as 75 °C thanks to the robust αRep building blocks. Since the α-helices of the brick and staple proteins are highly programmable, their design allows encoding the geometry and chemical surfaces of the final supramolecular protein architecture. This work opens routes toward the design and fabrication of multiscale protein origami with arbitrarily programmed shapes and chemical functions.