Expression, Purification, and Spectral Characterization of Phytochromes.

Expression and purification of recombinant proteins are important for the structure-function study of phytochromes. However, it is difficult to purify phytochrome proteins from natural sources or using a bacterial expression system, due to the presence of multiple phytochrome species and low expression and solubility, respectively. Here we describe the expression of recombinant full-length plant phytochromes in the yeast Pichia pastoris, and the spectral analysis of chromophore-assembled phytochromes before and after the purification by streptavidin affinity chromatography.