Development of an Engineered Photoactive Yellow Protein as a Cross-Linking Junction for Construction of Photoresponsive Protein-Polymer Conjugates

Based on a bacterial blue light photoreceptor, photoactive yellow protein (PYP), we have developed a photoresponsive protein module, Hpg5-PYP, bearing five alkynyl groups as reactive sites. We constructed a yellow-colored photoresponsive protein–polymer conjugate by using covalently bonded Hpg5-PYP with poly(N,N-dimethylacrylamide-co-2-hydroxy-3-azidopropyl methacrylate) (DMA-HAZPMA copolymer). Hpg5-PYP retained photoreactivity towards blue-light irradiation in the conjugate, and the conjugate showed a photoresponsive viscosity change upon irradiation with blue light at 25 °C. In contrast, a mixture of Hpg5-PYP and DMA-HAZPMA copolymer prepared for reference did not show any dependency of the viscosity on light irradiation, indicating the importance of crosslinking.