Homo‐ and heteropolymer self‐assembly of recombinant trichocytic keratins

Abstract

In the past two decades, keratin biomaterials have shown impressive results as scaffolds for tissue engineering, wound healing, and nerve regeneration. In addition to its intrinsic biocompatibility, keratin interacts with specific cell receptors eliciting beneficial biochemical cues. However, during extraction from natural sources, such as hair and wool fibers, natural keratins are subject to extensive processing conditions that lead to formation of unwanted by-products. Additionally, natural keratins suffer from limited sequence tunability. Recombinant keratin proteins can overcome these drawbacks while maintaining the desired chemical and physical characteristics of natural keratins. Herein, we present the bacterial expression, purification, and solution characterization of human hair keratins K31 and K81. The obligate heterodimerization of the K31/K81 pair that results in formation of intermediate filaments is maintained in the recombinant proteins. Surprisingly, we have for the first time observed new zero- and one-dimensional nanostructures from homooligomerization of K81 and K31, respectively. Further analysis of the self-assembly mechanism highlights the importance of disulfide crosslinking in keratin self-assembly.

Recent developments in sustainably sourced protein-based biomaterials

“…Biomimetic recombinant hagfish thread keratin [41], recombinant human hair keratins K31 and K81 [42,43].…”

Recombinant human hair keratin proteins for halting bleeding

“…These extraction procedures hardly control the amino acid composition and molecular weight (MW) of extracted keratins due to the random break of cystine bonds [10]. Besides, the properties of extracted proteins are critically dependent on the raw material sources [13]. The quality of human hair keratins is also difficult to control because perming and colouring hair are more and more popular [14].…”

“…Herein, we selected a type-I human hair keratin of K37 and a type-II human hair keratin of K81 for heterologous expression, and the haemostatic efficiency and mechanism of recombinant human hair keratin proteins were firstly assessed. Actually recombinant keratins have been previously produced to study the structure features and self-assembly process of intermediate filaments [13,18]. However, this study firstly described the heterologous expression of K37, and this is the first time recombinant keratin proteins were used in tissue engineering (haemostasis).…”

Self-Assembly of Solubilized Human Hair Keratins

“…Because of the abundance, versatility, and reduced risk of interspecies pathogen transfer, cysteine-rich human hair keratins have emerged as a viable biomaterial with various potential applications in biomedical sciences. − Understanding the intrinsic behavior, interactions, and self-assembly characteristics of soluble human hair keratins will be pivotal to harnessing the full potential of this material. Much of the current understanding of cross-linking and hierarchical self-assembly of keratin intermediate filaments (IFs) was gleaned from epithelial keratins, from which peptide domains involved in the assembly were identified. , However, little of the same is known about human hair keratins, including the expression profiles of the various subtypes and the interaction mechanisms between them, − with only limited work done on selected recombinant hair keratins . Herein, we report a method to induce the conformation change of hair keratin fibers by controlling the self-assembly process.…”