Structural, Mechanistic and Genomic Insights into OCP- Mediated Photoprotection - Advances in Botanical Research - page 8

Figure 1.1 The structure of the OCP. The N-terminal domain is uppermost, with the
backbone traced in red; the C-terminal domain is traced in red. The carotenoid is shown
in sticks as are all absolutely conserved amino acids among the 90 currently available
OCP sequences. Conserved water molecules are shown as spheres. Figure made with
pymol http://www.pymol.org/ ). See the colour plate.
In 2008, the OCP was shown to be a photoactive protein ( Wilson,
Punginelli, et al., 2008 ). In darkness, it is orange (OCP o ) and its absor-
bance spectrum shows two maxima at 476 and 496 nm, with a shoul-
der at 440 nm. Absorption of blue-green light converts, with a very low
yield, the OCP o form to a metastable red form (OCP r ) ( Wilson, Punginelli,
et al., 2008 ). The red-shifted spectrum of the OCP o loses the resolution of
the vibrational bands and shows a large maximum at 510 nm. The rates of