Fig. 2.

Current approaches to modifying the PSII core. Left panel: In PSII from cyanobacteria, algae and plants, the core subunits (circles) multiply interact (dotted lines) with each other and to a lesser extent with other transmembrane (rectangles) and peripheral (triangles) proteins. Middle panel: If core subunits in cyanobacteria (blue) are replaced by their plant pendants (green), their sequence differences may weaken or disrupt these interactions (thinner dotted lines), severely affecting the function of PSII. Right panel: Stephen Mayfield and co-workers [50] replaced an entire green algal PSII core with variants from other green algal species (indicated by a lighter shade of green). This would be expected to maintain the interactions between PSII core subunits, but might have affected interactions with other PSII proteins