FIGURE 4.

Carotenoid-protein interactions in the OCP and comparison of carotenoid conformations between A. maxima and Synechocystis OCP. A, the two molecules of Synechocystis wild type OCP in the crystallographic asymmetric unit are shown. The two domains are colored as in Fig. 2, and the molecule on the right contains the structurally conserved water molecules. Residues within 3.9 Å of the carotenoid are shown as gray sticks with polar atoms colored as in Fig. 2. Glycerol molecules are shown as yellow sticks. B, superposition of the ECN (orange) and 3′-hydroxyechinenone (blue) from the Synechocystis and A. maxima OCP structures. C, close-up of the carotenoid-protein interactions in the N-terminal domain; side chains and water molecules discussed throughout the text are labeled.