BRC-BIO: Harnessing sequence features to understand and manipulate the function of reflectin proteins in iridescence

Reflectin proteins are key components of light-scattering nanostructures in cephalopods such as squid and octopuses. A prominent example of these types of structures is the tunable and reversibly iridescent reflectors. These proteins are found within specialized cells, called iridocytes, present in the skin of certain squid species. Iridescence in these cells is driven by reversible phosphorylation of reflectins. Due to their fascinating properties, reflectins and the light-manipulating assemblies that contain them have served as bioinspiration for a range of work aiming to develop next-generation active biophotonic biomaterials and nanotechnologies. However, the molecular details of reflectin assembly, as well as the mechanisms and evolution of tunability, remains poorly understood. Reflectin proteins have a unique amino acid sequence that is likely critical in enabling them to serve their biophotonic functions. This project seeks to disentangle the effects of multiple features within reflectin's unique amino acid to its assembly properties and biophotonic function. Soka University of America undergraduates will receive scientific training and research experience as they work with the PI and contribute to this project. The PI will also engage a broader group of undergraduates in research by offering a Course-based Undergraduate Research Experience that enables students to participate in an authentic semester-long research project involving reflectins. Reflectins proteins are intrinsically disordered block copolymers. Recent work suggests that reflectin proteins undergo liquid-liquid phase separation to form biomolecular condensates. While condensate formation by many proteins has been linked to a range of cellular processes, reflectins are unique in their biological role as drivers of tunable biophotonics and in their observed ability to assemble into dynamically arrested spherical assemblies of predictable size. The PI and undergraduate coworkers will characterize reflectin proteins using a range of techniques including microscopy, light scattering, and more, to elucidate the hidden design principles that link reflectin's sequence to its assembly properties. These discovered design principles will then be applied to rationally re-engineer reflectin to improve its capability as a tunable biomaterial. The PI will extend the characterization of single- and multi-component reflectin condensates to within eukaryotic cells, elucidating how these proteins behave within more complex cellular environments. This project will offer insight into possible mechanisms for the evolution of tunable iridescence in loliginid squids and will also produce a deeper understanding of the molecular mechanisms that drive reflectin tunable assembly and dynamic arrest, providing knowledge that may be potentially applied towards the development of future biophotonic technologies and biomaterials. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.