Cyanobacterial Small Chlorophyll-binding Protein ScpD (HliB) Is Located on the Periphery of Photosystem II in the Vicinity of PsbH and CP47 Subunits

Abstract

Cyanobacteria contain several genes coding for small one-helix proteins called SCPs or HLIPs with significant sequence similarity to chlorophyll a/b-binding proteins. To localize one of these proteins, ScpD, in the cells of the cyanobacterium Synechocystis sp. PCC 6803, we constructed several mutants in which ScpD was expressed as a His-tagged protein (ScpDHis). Using two-dimensional native-SDS electrophoresis of thylakoid membranes or isolated Photosystem II (PSII), we determined that after high-light treatment most of the ScpDHis protein in a cell is associated with PSII. The ScpDHis protein was present in both monomeric and dimeric PSII core complexes and also in the core subcomplex lacking CP43. However, the association with PSII was abolished in the mutant lacking the PSII subunit PsbH. In a PSII mutant lacking cytochrome b 559 , which does not accumulate PSII, ScpDHis is associated with CP47. The interaction of ScpDHis with PsbH and CP47 was further confirmed by electron microscopy of PSII labeled with Ni-NTA Nanogold. Single particle image analysis identified the location of the labeled ScpDHis at the periphery of the PSII core complex in the vicinity of the PsbH and CP47. Because of the fact that ScpDHis did not form any large structures bound to PSII and because of its accumulation in PSII subcomplexes containing CP47 and PsbH we suggest that ScpD is involved in a process of PSII assembly/repair during the turnover of pigment-binding proteins, particularly CP47.

Psb28 Protein Is Involved in the Biogenesis of the Photosystem II Inner Antenna CP47 (PsbB) in the Cyanobacterium Synechocystis sp. PCC 6803

“…In this respect, it is interesting that the level of Psb28 is significantly decreased in the mutant lacking the PsbH protein (Fig. 3A), which was previously shown to be essential for the binding of Hli proteins to CP47 (Promnares et al, 2006). We therefore assume that the Psb28 binding site on CP47 is located in the vicinity of PsbH.…”

“…7). Recent results showing the association of so-called high light-induced proteins with PSII (Promnares et al, 2006;Yao et al, 2007) and their presumable role in the temporary binding of Chl during the PSII repair-related D1 replacement (Vavilin et al, 2007) indicate that Chl molecules released from the degraded D1 can be reused. It is possible that the lack of the newly synthesized CP47 allows more Chl precursors to be utilized for the synthesis of Chl consumed during selective D1 turnover.…”

A Cyanobacterial Chlorophyll Synthase-HliD Complex Associates with the Ycf39 Protein and the YidC/Alb3 Insertase

“…Deletion of the ferrochelatase CAB domain resulted in an aberrant accumulation of chlorophyll-protein complexes under high light, a phenotype not observed for other Hlip mutants (Sobotka et al, 2011). HliA, HliB, and HliC were found to interact with the PSII subunit CP47, likely to photoprotect the PSII assembly machinery and stabilize chlorophylls released during the process of PSII repair (Promnares et al, 2006;Yao et al, 2007). In contrast, HliD does not colocalize with PSII (Yao et al, 2007) but rather, as shown in this work, HliD copurifies with FLAG-ChlG (Figure 1).…”

Temporal dynamics of Prochlorococcus ecotypes in the Atlantic and Pacific oceans

“…This protein family, also called small cab-like proteins, aids in high-light survival and photoacclimation in Synechocystis (He et al, 2001;Havaux et al, 2003), and may also have a role in light-shock tolerance in eNATL. The mechanism by which they do this remains unclear, but high light-inducible proteins are thought to physically associate with either photosystem and allow it to shed excess energy as heat and thereby reduce photoinactivation (Promnares et al, 2006;Yao et al, 2007). As a photosynthetic organism, reducing and reversing the effects of photosystem inactivation is crucial for the survival of Prochlorococcus exposed to high light levels.…”