Fig. 1: Spectra and function of DrBphP and DrBphP-DrRR.

a The domain organization and the linker configuration are shown with the position of the biliverdin (BV) chromophore indicated. CA catalytic ATP-binding, DHp dimerization and histidine phosphotransfer, GAF cGMP phosphodiesterase-adenylate cyclase FhlA, HK histidine kinase, PAS Per-ARNT-Sim, PHY phytochrome-specific, PSM photosensory module, REC receiver domain, RR response regulator. b Absorption spectra of both proteins recorded in dark (D) or after saturating 655 nm red light (R). The spectra are normalized at the peak at 700 nm of the corresponding dark spectrum. Source data are provided as a Source Data file. c Dark reversion of DrBphP and DrBphP-DrRR. Response regulator fusion increases the DrBphP dark reversion, which resembles the addition of soluble DrRR to DrBphP (see Supplementary Fig. 1b)³⁵. Source data are provided as a Source Data file. d Phos-tag assay of phosphatase activity³⁵. In the assay, the retention of phosphorylated protein is slower than its non-phosphorylated counterparts. Here, all samples were supplemented with the same amount of phospho-DrRR (p-DrRR) and the change in its final amount implies either kinase (increase) or phosphatase (decrease) activity. The gel shows that DrBphP-DrRR dephosphorylates p-DrRR in its red light-illuminated state (lane R) and the activity is stalled in the darkness (lane D). The phosphatase activity of the fusion protein resembles that of DrBphP, although is generally weaker because of competition between the fused and free DrRR. See Supplementary Fig. 1c for an extended gel. Source data are provided as a Source Data file.