Mutational analysis of the pea phytochrome A chromophore pocket: chromophore assembly with apophytochrome A and photoreversibility

Mutational analysis of single amino acid substitutions of residues adjacent to Cys-323 in the mutants of pea apophytochrome A revealed the interactions between the chromophore and the apoprotein which led to photoreversible absorbance changes. Results derived from the analysis of the mutants for kinetics of chromophore adherence and spectral features of phycocyanobilin (PCB)-holophytochromes were consistent with the theoretical results of phytochrome structural models. The autocatalytic potential of apophytochromes to attach PCB indicates the non-occurrence of major disturbances/changes in the apoproteins.