Figure 1. T. elongatus PSIIcc dimers viewed.

(A) from the cytoplasmic side and (B) from the membrane. The reaction centre transmembrane subunits D1/D2, the internal antennae (CP43/CP47, omitted in the left monomer) and the membrane extrinsic subunits PsbU/V/O are highlighted in color. Small transmembrane subunits comprising a single α-helix (two for PsbZ) are indicated by single letter referring to the PsbH-Y proteins and ycf12. Q_A/B denote the plastoquinone cofactor, Fe the non-heme iron. The site of the water-oxidizing complex (WOC, Mn₄CaO₅) within each monomer is shown by the black box. (C) Electron density map (1σ 2F_o-F_c) at the depleted WOC site (shown for the locked dimer, discussed below). Free coordinating residues from the D1 subunit (cream) and CP43 (green) are shown alongside Arg357(CP43) and His 337(D1), which are within hydrogen-bond distance to cluster oxygen atoms in Umena et al. (2011), (PDB:3WU2).

DOI: http://dx.doi.org/10.7554/eLife.26933.002

Figure 1—figure supplement 1. Effect of NH₂OH-EDTA treatment performed on dPSIIcc solutions.

(A) SDS-PAGE profiles showing the completeness of large PSII subunits in C₁₂E₈ dPSIIcc solutions before (lane 1) and after (lane 2, lane 3 and lane 4) size exclusion chromatography. The dPSIIcc samples were incubated with variable NH₂OH/EDTA concentrations in darkness at 4°C for 1–2 hr and then washed three times with MCB buffer without CaCl₂. The samples were treated with 0 mM (lane 1, lane 2), 20 mM (lane 3) and 50 mM (lane 4) NH₂OH/EDTA. After the treatment as described above PSII samples at 0 mM, 20 mM and 50 mM NH₂OH/EDTA were eluted from a size exclusion column shown in lane 2, 3 and 4. B: Gel filtration chromatogram showing the effect of NH₂OH/EDTA (50 mM) treatment on monomerization of C₁₂E₈ dPSIIcc solution (left panel). Untreated C₁₂E₈ dPSIIcc (red, dotted line) and ßDM PSII monomer (blue, dotted line) are used as references. The treated C₁₂E₈ dPSIIcc solution using 50 mM NH₂OH/EDTA is represented in black. BN-PAGE profiles using the same sample were obtained after gel filtration (right panel).

DOI: http://dx.doi.org/10.7554/eLife.26933.003