Spectroscopic Characteristics of Photosynthetic Cryptophyte Algae: Recombinant Phycobiliproteins and Protein Subunits

Abstract

The unique spectroscopic properties of cryptophyte algae phycobiliproteins have been used to elucidate light harvesting and energy transfer mechanisms in biological systems. The spectroscopic characteristics of the subunits of the phycobiliprotein PC645 have yet to be extensively studied. Using ultraviolet-visible spectroscopy, the novel absorption characteristics of the subunits of PC645 were revealed and provided support for the presence of energy transfer between the chromophore bilins in the protein. In addition, the formation of non-native phycobiliproteins has not been attempted in the literature. By swapping the α/β subunits of the phycobiliproteins PE545 and PC645, artificial recombinant phycobiliproteins were formed, and their absorption characteristics were measured. The recombinant protein PC645α + PE545β did not display significantly unique spectral features that provide evidence for the successful folding of the chimeric protein. However, the recombinant protein PE545α + PC645β showed a blue-shifted absorption spectrum, revealing the production of a chimeric phycobiliprotein and suggesting the presence of energy transfer between its bilin chromophores. The conservation of structure across the various α/β subunits can be utilized to create new energy transfer pathways and directly modify biological systems to harvest particular wavelengths of light.