Differences between the surface properties of the P_R and P_FR forms of native pea phytochrome, and their application to a simplified procedure for purification of the phytochrome

The ability of phytochrome from etiolated pea shoots (Pisum sativum L. cv. Alaska) to bind to various chromatographic adsorbents and its mobility during non-denaturing electrophoresis were examined with phytochrome in either the red light-absorbing form (PR) or the far-red light-absorbing form (P_FR). Preferential binding of P_FR to modified hydrophilic polyvinyl resins, such as butyl Toyopearl, phenyl Toyopearl, Blue Toyopearl (Cibacron Blue F3G-A conjugated) and Red Toyopearl (Procion Red HE-3B conjugated), was observed. A simplified method for purification of native phytochrome was developed based on the properties of P_R and P_FR. P_FR bound preferentially to the hydrophobic adsorbents, to indicate that the surface of P_FR is more hydrophobic than that of P_R. A difference in net surface charges between P_R and P_FR was detected by an analysis based on the different mobilities of the two forms during non-denaturing polyacrylamide gel electrophoresis in gels prepared with various concentrations of polyacrylamide. The apparent molecular weights of P_R and P_FR, estimated from the analysis, were 378 and 419 kilodaltons, respectively. The difference suggests that a significant change in molecular shape occurs during the photoconversion. The differences in surface properties of P_R and P_FR are discussed.