Fig. 1: Variability of carotenoid absorption in OCP and its variants.
A Absorption spectra of OCP and sequence variants thereof in 0.8 M phosphate. The inset shows the fractional content of the orange photoactive form. Asterisks represent OCP species not forming the orange state upon expression and purification from ECN/CAN producing E. coli strains; the orange compact forms of CAN-containing OCPYY and OCPAW appeared only in 0.8 M phosphate. “COCP” corresponds to the individual OCP-CTD forming a dimer coordinating CAN. B, C decomposition of the absorption spectra of the compact forms of WT OCP (B) and the OCPWW variant (C) corresponding to the central positions of the elution peaks (apparent Mw ~35 kDa) on analytical SEC with full-spectrum detection. To estimate the yield of distinct spectral states, the absorption spectrum of the photoactivated protein was subtracted from the dark-adapted sample with an appropriate scaling factor. Numbers indicate the percentage of the orange and red states.
