Fig. 4: PIF6 increases the Pr→Pfr photoconversion efficiency of phyB.
From: Structural insight into PIF6-mediated red light signal transduction of plant phytochrome B
a Close-up view of PIF6N structure in phyB-Pfr‒PIF6β complex. The upper panel shows the sequence and the secondary structure of PIF6N. The β1-sheet in the PIF6N interacts with and stabilizes the NTE of the phyB-Pfr protomer A (in light blue). PIF6N denotes N-terminus of PIF6β (residues 1‒60). b Proteins used in c‒f were subjected to SDS-PAGE, and gels were stained for protein with Coomassie blue (left panel) or for covalently bound PΦB by zinc-induced fluorescence (right panel). c UV–vis absorbance spectra of phyB alone, phyB + PIF6β, and phyB + PIF6β3 mut in the dark (dark lines) and under red light-irradiation (red lines) are shown. The Pr→Pfr difference spectra are shown at 70% magnitude. The SCRs of phyB alone, phyB + PIF6β, and phyB + PIF6β3 mut are 0.903, 0.862, and 0.898, respectively. Spectra are the average of three technical replicates. PIF6β3 mut indicates a PIF6β mutant which contains E19A, R42A, and I46A triple mutation sites. d Pr→Pfr photoconversion of phyB alone, phyB + PIF6β, and phyB + PIF6β3 mut at 25 °C under red light irradiation (617 μmol m−2 s−1) and monitored at 720 nm. e Pfr→Pr photoconversion of phyB alone, phyB + PIF6β, and phyB + PIF6β3 mut with far-red light (655 μmol m−2 s−1) and monitored at 665 nm and 720 nm. f Representative kinetics of Pfr→Pr thermal reversion at 25 °C. The amount of phyB-Pfr remaining after 400 mins is 8 times higher in the presence of the PIF6β. Lines reflect single- or double-exponential kinetic fits as appropriate to the data. Rate constants and amplitudes are provided in Supplementary Tables S2 and S3.
