Assessing in vitro Assembly of Mutant D. Opalescens Reflectin Proteins

Surge 171

Cephalopod iridescence serves as effective intra- and interspecific communication and has long been looked at for the possibility of application in biophotonic materials. Reflectin proteins, found in the iridocytes of cephalopods, can allow for tunable iridescence in certain squid. The deep invaginations into the iridocytes act as a Bragg reflector, with the condensation and subsequent assembly of reflectin causing a change in refractive index and thickness of the invagination, resulting in a change in the wavelength of refracted light. The assembly is reversible and mediated by phosphorylation in vivo but details of the precise assembly process have yet to be elucidated. Here, we investigate the role of tyrosine phosphorylation at two specific sites on D. opalescens reflectin A1 protein. We show that glutamate substitution and insertion mutants at both sites to mimic the negative charge of a phosphate group in vivo result in larger assembly size (observed by dynamic light scattering) than wild-type. These results show that reflectin assembly may be mediated by the overall net neutrality of the protein. This finding may contribute to applications of the protein in tunable biological thin films or other materials.