Hydrogel Biopolymer Created from the Self-Assembly of a Designed Protein Containing a Four-Helix Bundle Forming Motif

Abstract

A protein hydrogel system based on the assembly of a four-helix bundle motif was proposed and synthesized by genetic engineering methods. This new polypeptide, named GBH1, consists of identical amphipathic helices of 22 residues in length oriented in opposite fashion to one another at each end of a polypeptide with a total length of 227 amino acids. The middle portion of the polypeptide (residues 79-147) is an unstructured random coil. The region between the amphipathic and unstructured segment is an α-helical stretch (23-78 and 148-204) not possessing a sequence compatible with a coiled-coil conformation, but rather possesses regions that have overwinding of the helix. The thermal unfolding of GBH1 shows more than one inflection point (T(m1) = 30.5 °C, T(m2) = 64.6 °C), indicative of a partially unfolded intermediate and, thus, multiple interactions in the folded state. A qualitative assessment of hydrogel formation with varying pH showed that acidic conditions did not support the gel state, indirectly indicating that the proposed four-helix bundle is the major cross-linking structure and not a leucine zipper motif. Scanning electron microscopy reveals a network of interacting protein molecules forming a spongelike matrix with numerous pores that would be occupied with water molecules.

Amphiphilic Elastin-Like Block Co-Recombinamers Containing Leucine Zippers: Cooperative Interplay between Both Domains Results in Injectable and Stable Hydrogels

“…8−10 The first Z-based selfassembled hydrogel was developed by Petka et al, 11 and since then, further research in this area has resulted in additional examples being reported. 8,9,12 Despite this, further optimization is still required for real applications. For example, the instability of these hydrogels has always been a handicap, presumably due to the highly hydrophilic environment created by the aqueous media contained within the hydrogel and, in many cases, gel formation has been qualitatively assessed, and with just a few exceptions, quantitative measurement using rheological methods has proved elusive.…”

Tunable Mechanical Properties of Ultrasmall Peptide Hydrogels by Crosslinking and Functionalization to Achieve the 3D Distribution of Cells

“…One example is Ac‐LIVAGK (LK 6 ). Due to its shortness, these peptides should be a cheaper alternative to other protein‐22, 23 or peptide‐based matrices with longer sequences, e.g., RADA‐1624 (PuraMatrix™), MAX125–27 and others 28, 29…”

Physics of engineered protein hydrogels

“…50 Depending on the coiled-coil sequence used, multiple unfolding transitions may also be observed, suggestive of intermediate states between fully aggregated and fully disordered with a lower degree of aggregation. 51 Cylindrical aggregates identified by SAXS for tetrameric coiled-coils persist above the dilute solution coiled-coil melting temperature, further indicating that the dissociation transition may be concentration dependent. The mechanical properties of coiled-coil and other associating protein hydrogels show rheology typically for physically associating polymer gels (Fig.…”