Role of the PB-loop in ApcE and phycobilisome core function in cyanobacterium Synechocystis sp. PCC 6803

Revisiting cyanobacterial state transitions

“…41,43 In the ApcE-C190S and the PB-loop ApcE Synechocystis mutants, the energy transfer from PBS to the photosystems is significantly affected. 43,44 However, state transitions in the former are not impaired, 91 while they appear to be decreased in the latter. 44 It has been proposed that the impairment of state transitions in the ΔApcD Synechocystis mutant is due to a permanent binding of PBS to PSII, which increases the PSII antenna even in darkness and PSII illumination (when the PQ pool is reduced).…”

“…43,44 However, state transitions in the former are not impaired, 91 while they appear to be decreased in the latter. 44 It has been proposed that the impairment of state transitions in the ΔApcD Synechocystis mutant is due to a permanent binding of PBS to PSII, which increases the PSII antenna even in darkness and PSII illumination (when the PQ pool is reduced). 41 This hypothesis can explain the relatively high fluorescence observed in the dark-adapted ΔApcD Synechocystis cells.…”

“…Mutations in ApcD, ApcF 40,41,51,85 and a particular domain of ApcE 44 affect state transitions in several cyanobacterial strains (Table 3). 40 suggested that in the ΔApcD Synechococcus PCC 7002 mutant, the inhibition of state transitions was due to a permanent decrease in energy transfer from PBS to PSI.…”

“…Mutations in the PBS terminal emitters affect the energy transfer to one or both photosystems in different cyanobacterial strains (see discussion in following sections). [40][41][42][43][44] The entire scientific community agrees that in cyanobacteria, like in plants and green algae, state transitions are triggered by redox changes in the PQ pool. 45,46 However, no agreement can be found in literature about the molecular mechanism, the sensor of the PQ redox state, or the signaling pathways involved.…”

Rates and pathways of energy migration from the phycobilisome to the photosystem II and to the orange carotenoid protein in cyanobacteria

“…PBS cores were isolated from the disrupted CK‐mutant cells by sucrose density gradient ultracentrifugation as it was described earlier . PSII complexes were obtained from the thylakoid membranes of PAL mutant solubilized by n ‐dodecyl‐β‐ d maltoside using one‐step chromatography (Toyopearl DEAE 650 S resin; Tosoh, Tokyo, Japan) according to the protocol described by Kern et al .…”