Chromopeptides from phytochrome. The structure and linkage of the PR form of the phytochrome chromophore

Abstract

The isolation and chromatographic purification of chromophore-containing peptides from the P_R form of phytochrome treated with pepsin and thermolysin are described. From the amino acid sequence and ¹H NMR spectral analysis of phytochromobiliundeca peptide (2), the structure of the P_R phytochrome chromophore and the nature of the thioether linkage joining pigment to peptide have been established. Furthermore, confirmatory evidence was obtained from similar analysis of phytochromobilioctapeptide (3). The implications of this structural assignment with respect to the mechanism of the P_R to P_FR phototransformation are considered.