Controlled nanometric fibers of self-assembled designed protein scaffolds

Abstract

The use of biological molecules as platforms for templating and nanofabrication is an emerging field. Here, we use designed protein building blocks based on small repetitive units (consensus tetratricopeptide repeat - CTPR) to generate fibrillar linear nanostructures by controlling the self-assembly properties of the units. We fully characterize the kinetics and thermodynamics of the assembly and describe the polymerization process by a simple model that captures the features of the structures formed under defined conditions. This work, together with previously established functionalization potential, sets up the basis for the application of these blocks in the fabrication and templating of complex hybrid nanostructures.

Dissecting and reprogramming the folding and assembly of tandem-repeat proteins

“…Exploiting these properties, one can extend the modular design process from individual repeat proteins to the assembly of repeat proteins into novel biomaterials with encoded properties and precisely displayed functional sites. To date, examples of this exciting field includes using metals, peptide binding, native chemical ligation and disulfide bonding to assemble repeat proteins into gels, films and fibres (Figure 4) [26][27][28]. One interesting design aspect that is peculiar to linear repeat proteins is the potential to change the shape of the super-helix (curvature, twist, pitch).…”

“…are indicated by different shaped pieces. Examples of published triggers for association are (A and H) chemical-induced polymerization of CTPR modules using native chemical ligation and disulfide bond formation [27,28], (B and H) metal-induced polymerization using minimized β-roll motifs on addition of La 2 + [30], (C and I) thick film formation after large, rigid super-helical 18 CTPR module proteins were deposited on a teflon surface with a plasticizer and left to dry (rectangles of alternating blue and green of three module units denote the extending super-helix [31]), (D and J) hydrogel formation of the same CTPR18 combining with multivalent cognate peptide-PEG cross-linker (pink circles on black lines) [26], (E and K) reversible gelation of a chimera of a leucine zipper (black and red rectangles) with designed minimized β-roll motifs. On addition of Ca 2 + (yellow circles) the minimized β-roll motifs fold (green squares) from unstructured polypeptides and oligomerize [32].…”

Biomolecular templating of functional hybrid nanostructures using repeat protein scaffolds

“…These self-assembly properties have been recently exploited to generate different CTPR-based assemblies, including hydrogels, nanofibres and thin films ( Figure 2) [38][39][40][41]. Protein thin nanofibres were obtained taking advantage of the head-to-tail interactions between proteins to drive the polymerization of the CTPR units ( Figure 2).…”

“…Protein thin nanofibres were obtained taking advantage of the head-to-tail interactions between proteins to drive the polymerization of the CTPR units ( Figure 2). Specific reactivities are introduced at both N-and C-terminal ends of the proteins in different ways to act as staple of the interaction [39,40]. The detailed characterization and modelling of the step growth polymerization process will allow to achieve full control in the fibre formation [39] and the generation of nanorods of defined lengths.…”

“…Specific reactivities are introduced at both N-and C-terminal ends of the proteins in different ways to act as staple of the interaction [39,40]. The detailed characterization and modelling of the step growth polymerization process will allow to achieve full control in the fibre formation [39] and the generation of nanorods of defined lengths. Ordered solid films made of CTPRs were obtained taking advantage of the self-assembly properties under water evaporation of a highly concentrated protein solution [38].…”