The ferredoxin docking site of photosystem I

Abstract

The reaction center of photosystem I (PSI) reduces soluble ferredoxin on the stromal side of the photosynthetic membranes of cyanobacteria and chloroplasts. The X-ray structure of PSI from the cyanobacterium Synechococcus elongatus has been recently established at a 2.5 A resolution [Nature 411 (2001) 909]. The kinetics of ferredoxin photoreduction has been studied in recent years in many mutants of the stromal subunits PsaC, PsaD and PsaE of PSI. We discuss the ferredoxin docking site of PSI using the X-ray structure and the effects brought by the PSI mutations to the ferredoxin affinity.

Lateral Segregation of Photosystem I in Cyanobacterial Thylakoids

“…The F x Fe 4 S 4 cluster sits near the cytoplasmic surface of the membrane, and the F A and F B iron-sulfur centers are held outside the bilayer to facilitate electron transfer to the extrinsic acceptor ferredoxin that docks onto the PsaC, PsaD, and PsaE subunits (Sétif et al, 2002). Figure 2G (right) shows the transmembrane location of the antenna chlorophylls and carotenoids.…”

“…Fourth and fifth subunits, PsaD and PsaE, are located either side of PsaC on the cytoplasmic side of the complex and in combination with PsaC provide the binding site for ferredoxin (Sétif et al, 2002). PsaD is also involved in the assembly of PSI and is necessary for the insertion of PsaC, PsaE, and of a sixth subunit, PsaL, into the complex (Xu et al, 2001).…”

A Program for Iron Economy during Deficiency Targets Specific Fe Proteins

“…5A). However, a stronger effect on protein levels was observed for PSAD, which mediates interactions between the PSI core and ferredoxin but does not bind Fe itself (Sétif et al, 2002), and which was reduced to one-half of the control levels at day 7 of depletion. In comparison to the two photosystems, the effect of Fe depletion was stronger and observed earlier for subunits of the cytochrome-b 6 /f complex.…”

In Planta Mutagenesis of Src Homology 3 Domain-like Fold of NdhS, a Ferredoxin-binding Subunit of the Chloroplast NADH Dehydrogenase-like Complex in Arabidopsis

“…A key to elucidating the function of NdhS in the chloroplast NDH complex was the finding that the predicted tertiary structure of the C-terminal domain of NdhS forms an SH3-like domain that is similar to that of PsaE, which forms the Fd-binding site of PSI with PsaC and PsaD (12,39). In cyanobacteria, PsaE was reported to be involved in CET in unspecified manner (40).…”

“…Besides PsaE, PsaC and PsaD also contribute to Fd binding (39). Similarly, NdhS is required for high affinity binding of NDH to Fd.…”