Inter-domain crosstalk in the phytochrome molecules

Phytochrome Phosphorylation Modulates Light Signaling by Influencing the Protein–Protein Interaction[W]

“…In fact, the Ser598 phosphorylation was thought to play an active role in the phyA-mediated lightsignal transduction (Lapko et al, 1999;Park et al, 2000;Kim et al, 2002b). Here, we showed that the transgenic plants of the S598A mutant were hypersensitive to light.…”

“…Despite considerable progress in defining the photosensory roles of phytochromes based on the structure-function relation, the primary biochemical mechanism by which the phytochrome molecule transduces the perceived light signals into cellular responses remains to be elucidated (Elich and Chory, 1997a;Park et al, 2000;Smith, 2000;Kim et al, 2002b). This study provides evidence for the regulatory function of phytochrome phosphorylation in the phytochrome-mediated light signaling in plants.…”

“…For the phytochrome Pr/Pfr phototransformation, we proposed that the primary step of phytochrome signaling involves phototransformation-dependent conformational changes (Park et al, 2000;Kim et al, 2002b). On Pr/Pfr phototransformation, the NTE region undergoes a conformational change from random coil to amphiphilic a-helix, which then interacts with the chromophore in the Pfr form (Parker et al, 1992;Deforce et al, 1994).…”

“…Also, two Trp residues near the core regulatory region of oat phyA become preferentially exposed in the Pfr form (Wells et al, 1994). Based on these results, it was proposed that part of the NTE chain interacts with the regulatory C-terminal core motif in the Pr form (switch off conformation) (Park et al, 2000;Kim et al, 2002b). After the Pr/Pfr phototransformation (switch on conformation), the NTE chain is withdrawn by its interaction with the chromophore, exposing and thus activating the regulatory core motif (or Quail box) for the interaction with PIPs to initiate the signal transduction cascade.…”

“…Ser17 is phosphorylated primarily in a Pr preferential manner, whereas Ser598 phosphorylation is preferred in the Pfr form (McMichael and Lagarias, 1990;Lapko et al, 1996). Because this Ser598 residue is phosphorylated only in the Pfr form that is considered the active form of phytochrome, it was suggested that the phosphorylation and dephosphorylation of Ser598 serves as a switch in phytochrome signaling (Park et al, 2000;Kim et al, 2002b).…”