MODELS FOR THE PHOTOREVERSIBILITY OF PHYTOCHROME. Z,E ISOMERIZATION OF CHROMOPEPTIDES FROM PHYCOCYANIN AND PHYTOCHROME.

Article abstract of DOI:10.1016/S0040-4020(01)88709-3

Chromopeptides which contain linear tetrapyrrole chromophores are prepared by proteolytic digestion of phycocyanin and phytochrome (P_r and P_fr forms).After the nucleophilic addition of mercaptoethanol to C-10 of the tetrapyrrole, irradiation with white light leads to photoisomerization of the tetrapyrrole (Z->E).The products prepared from (Z)-phycocyanin and P_r chromopeptides are similar to P_fr chromopeptides with respect to chromatographic properties, electronic spectra and photolability.It is concluded that the linear tetrapyrrole chromophore of P_r is all-Z whereas P_fr has the E configuration at one of the bridges.