Figure 4.

Ferredoxin-binding and Fe-S cluster distances in Synechococcus 7335 FRL-PSI.A, stromal view of the stromal ridge where Fd is bound. B, surface electrostatics maps from the cryo-EM models showing the core without Fd (top), the Fd alone (middle), and the binding location of the Fd (bottom). C, side view of the stromal ridge with Fd bound. The cartoons are made slightly transparent, and the Fe-S clusters are shown in sphere representation. Both center-to-center distances (solid black lines and font color) and edge-to-edge distances (dashed red lines and font color) are shown. Edge-to-edge distances include the S atoms from coordinating Cys sidechains. Fd, ferredoxin; FRL, far-red light; PSI, photosystem I.