Structure, self-assembly, and properties of a truncated reflectin variant
Significance The investigation of protein-based materials has provided a better understanding of living systems and has led to the development of ubiquitous modern technologies. Within this context, unique cephalopod proteins called reflectins have exhibited promise for biophotonics and bioelectronics applications, but the exploration of reflectins as materials has been hindered by an incomplete understanding of their structures and properties. Here, we resolve the molecular-level structure of a model reflectin variant, establish a straightforward approach to controlling the assembly of this protein, and describe a correlation between its structural characteristics and light-manipulating properties. Taken together, our findings advance current understanding of reflectin-based materials, provide insight into the color-changing capabilities of cephalopods, and afford new opportunities in biochemistry, cellular biology, bioengineering, and optics. Naturally occurring and recombinant protein-based materials are frequently employed for the study of fundamental biological processes and are often leveraged for applications in areas as diverse as electronics, optics, bioengineering, medicine, and even fashion. Within this context, unique structural proteins known as reflectins have recently attracted substantial attention due to their key roles in the fascinating color-changing capabilities of cephalopods and their technological potential as biophotonic and bioelectronic materials. However, progress toward understanding reflectins has been hindered by their atypical aromatic and charged residue-enriched sequences, extreme sensitivities to subtle changes in environmental conditions, and well-known propensities for aggregation. Herein, we elucidate the structure of a reflectin variant at the molecular level, demonstrate a straightforward mechanical agitation-based methodology for controlling this variant’s hierarchical assembly, and establish a direct correlation between the protein’s structural characteristics and intrinsic optical properties. Altogether, our findings address multiple challenges associated with the development of reflectins as materials, furnish molecular-level insight into the mechanistic underpinnings of cephalopod skin cells’ color-changing functionalities, and may inform new research directions across biochemistry, cellular biology, bioengineering, and optics.