Protein structures evolved through a complex interplay of cooperative interactions and it is still very challenging to design new protein folds de novo. Here, we present a strategy to design self-assembling polypeptide nanostructured polyhedra, based on modularization using orthogonal dimerizing segments. We designed end experimentally demonstrated formation of the tetrahedron that self-assembles from a single polypeptide chain comprising 12 concatenated coiled-coil-forming segments separated by flexible peptide hinges. Path of the polypeptide chain is guided by the defined order of segments that traverse each of the 6 edges of the tetrahedron exactly twice, forming coiled-coil dimers with their corresponding partners. Coincidence of the polypeptide termini in the same vertex is demonstrated by reconstitution of the split fluorescent protein by the polypeptide with the correct tetrahedral topology, while polypeptides with a deleted or scrambled segment order fail to self-assemble correctly. This design platform provides the basis for construction of new topological polypeptide folds based on the set of orthogonal interacting polypeptide segments.

Biopolymers, the essential components of life, are able to form many complex nanostructures, and proteins in particular are the material of choice for most cellular processes. Owing to numerous cooperative interactions, rational design of new protein folds remains extremely challenging. An alternative strategy is to design topofolds-nanostructures built from polypeptide arrays of interacting modules that define their topology. Over the course of the last several decades DNA has successfully been repurposed from its native role of information storage to a smart nanomaterial used for nanostructure self-assembly of almost any shape, which is largely because of its programmable nature. Unfortunately, polypeptides do not possess the straightforward complementarity as do nucleic acids. However, a modular approach can nevertheless be used to assemble polypeptide nanostructures, as was recently demonstrated on a single-chain polypeptide tetrahedron. This review focuses on the current state-of-the-art in the field of topological polypeptide folds. It starts with a brief overview of the field of structural DNA and RNA nanotechnology, from which it draws parallels and possible directions of development for the emerging field of polypeptide-based nanotechnology. The principles of topofold strategy and unique properties of such polypeptide nanostructures in comparison to native protein folds are discussed. Reasons for the apparent absence of such folds in nature are also examined. Physicochemical versatility of amino acid residues and cost-effective production makes polypeptides an attractive platform for designed functional bionanomaterials.

Bionanotechnology seeks to modify and design new biopolymers and their applications and uses biological systems as cell factories for the production of nanomaterials. Molecular self-assembly as the main organizing principle of biological systems is also the driving force for the assembly of artificial bionanomaterials. Protein domains and peptides are particularly attractive as building blocks because of their ability to form complex three-dimensional assemblies from a combination of at least two oligomerization domains that have the oligomerization state of at least two and three respectively. In the present paper, we review the application of polypeptide-based material for the formation of material with nanometre-scale pores that can be used for the separation. Use of antiparallel coiled-coil dimerization domains introduces the possibility of modulation of pore size and chemical properties. Assembly or disassembly of bionanomaterials can be regulated by an external signal as demonstrated by the coumermycin-induced dimerization of the gyrase B domain which triggers the formation of polypeptide assembly.

No abstract

No abstract