FIGURE 8.

Implications of the interaction between CyanoP and the D1 C-terminus. (A) Comparison of the suggested position of CyanoP with the coordination environment of the OEC. D1 is shown in ribbon presentation (a-loop: pink, c-loop: orange, C-terminus: red, transmembrane helices: gray). The ligands including the two residues of CP43 are depicted as sticks, whereas the atoms of the cluster are shown as spheres (oxygen: red, manganese: purple, calcium green). The 13 C-terminal residues of D1 are wound around the OEC and bury the c-loop. If this region adopts a more outstretched conformation in the absence of the OEC, a broad interaction interface with CyanoP is possible. Moreover, the c-loop can be accessed by free metal ions required for the assembly of the OEC. (B) Analysis of conserved residues on the surface of CyanoP (Michoux et al., 2010; pdb code: 2XB3) based on a previous study (Jackson et al., 2012). The Consurf-Server (Landau et al., 2005) identified a highly conserved groove on the surface of CyanoP representing an ideal binding site for the D1 C-terminus. Residues with the first and second highest degree of conservation are shown in yellow, the third highest degree in pale yellow and all other residues in gray.