Figure 2.

Bilin Chromophores and Absorption Spectra of Representative Phys within the Superfamily.

(A) Chemical structure and apoprotein thioether linkage position for various bilins used in Phys. The four pyrrole rings (A-D) and important carbon positions in the bilin are indicated.

(B) Chemical structure and dual thioether linkage specific to CBCRs with blue/green photocycles.

(C) Absorption spectra of the dark-adapted (D) and photoactivated states after blue (B), far-red (FR), green (G), red (R), and violet (V) excitation for canonical Phys with Pr dark-adapted states (At-PhyB, Syn-Cph1, and Dr-BphP), a bathy-Phy (Pa-BphP), a Pnr Phy (Rp-BphP3), a PAS-less Phy (Syn-Cph2), and three CBCRs (Te-PixJ, Np-F2164, and Syn-CcaS). Dashed lines denote the photoactivated state. The bilin type is indicated in parenthesis for each Phy. Absorption maxima are indicated.