Supramolecular Assembly and Small-Molecule Binding by Protein-Engineered Coiled-Coil Fibers

Abstract

The ability to engineer a solvent-exposed surface of self-assembling coiled coils allows one to achieve a higher-order hierarchical assembly such as nano-or microfibers. Currently, these materials are being developed for a range of biomedical applications, including drug delivery systems; however, ways to mechanistically optimize the coiled-coil structure for drug binding are yet to be explored. Our laboratory has previously leveraged the functional properties of the naturally occurring cartilage oligomeric matrix protein coiled coil (C), not only for its favorable motif but also for the presence of a hydrophobic pore to allow for smallmolecule binding. This includes the development of Q, a rationally designed pentameric coiled coil derived from C. Here, we present a small library of protein microfibers derived from the parent sequences of C and Q bearing various electrostatic potentials with the aim to investigate the influence of higher-order assembly and encapsulation of candidate small molecule, curcumin. The supramolecular fiber size appears to be well-controlled by sequence-imbued electrostatic surface potential, and protein stability upon curcumin binding is well correlated to relative structure loss, which can be predicted by in silico docking.

Tuning a coiled-coil hydrogel via computational design of supramolecular fiber assembly

“…27 We have also recently shown that Q2 and Q dock CCM similarly by in silico models using Rosetta where Q2 and Q possess interface scores of −46.3 kcal mol −1 and −46.2 kcal mol −1 , respectively. 35 The similar ATR-FTIR and behavior of CCM-bound Q2 shown here further confirm that CCM exhibits a positive interaction inside the hydrophobic pore of the coiled-coil eliciting an increase in α-helicity and stability.…”

“…Design Q2 was previously designed 35 to assemble into thinner nanofibers relative to Q by reduced lateral supramolecular assembly (Fig. 1).…”

Fluorescent azobenzene-confined coiled-coil mesofibers

“…Previously, similar drug binding studies have been completed with the hydrophobic small molecule, curcumin (CCM). 15 CCM is known to induce fiber thickening in collagen and Q. 14,16,17 We hypothesize that a similar mechanism occurs between AzoCholine and Q where binding of AzoCholine causes exposure of nonpolar groups and increased surface activity in Q, which further drives its fiber aggregation.…”

Genetic Fusion of Thermoresponsive Polypeptides with UCST‐type Behavior Mediates 1D Assembly of Coiled‐Coil Bundlemers

“…[1a, 17] Alpha-helical coiled-coil peptides have been shown to be particularly useful, [18] and have been utilized to generate nanofibrillar assemblies by modulating the solvent-exposed surface of the coiled-coils. [19] Recently, the Saven group has computationally designed peptides to form antiparallel, tetrameric coiled coils, or "bundlemers", with dimensions corresponding to a nanoscopic cylinder of 2 nm × 4 nm; [20] these sequences have been produced by both solid-phase and recombinant methods. [20a, 21] While unmodified bundlemers are unable to assemble into long 1D fibrils alone, [22] covalent reaction of bundlemers with complementary functional groups yields bundlemer polymers with extreme chain stiffness and contour lengths of a few micrometers, [20a] establishing these coiled coil-forming peptides as excellent building blocks for creating programmable, peptide-based, and structurally robust 1D and 2D nanostructures.…”

“…In contrast, short self‐assembling peptides from structural proteins have been widely employed in the generation of assembled materials for use as drug carriers, gene‐targeting therapeutics, templating of inorganic molecules, and fabrication of structured materials [1a, 17] . Alpha‐helical coiled‐coil peptides have been shown to be particularly useful, [18] and have been utilized to generate nanofibrillar assemblies by modulating the solvent‐exposed surface of the coiled‐coils [19] . Recently, the Saven group has computationally designed peptides to form antiparallel, tetrameric coiled coils, or “bundlemers”, with dimensions corresponding to a nanoscopic cylinder of 2 nm×4 nm; [20] these sequences have been produced by both solid‐phase and recombinant methods [20a, 21] .…”