Isolation, Characterization and Electron Microscopy Analysis of A Hemidiscoidal Phycobilisome Type from the Cyanobacterium <i>Anabaena</i> sp. PCC 7120

Ducret, Axel; Sidler, Walter; Wehrli, E.; Frank, Gerhard; Zuber, Herbert

doi:10.1111/j.1432-1033.1996.01010.x

Cited by 66 publications

(55 citation statements)

References 63 publications

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“…The two half core cylinders C1 and C2 are unique. In contrast to half core cylinders arranged in a side-by-side manner with other core cylinders in early models [5], C1 and C2 are arranged perpendicularly to the other core cylinders ( Figure 1A). In addition, these half core cylinders have connections to all other PBS components (core cylinders A1, A2, and B, and all peripheral rods), suggesting that they are important in the overall organization of this PBS.…”

Section: Overall Structures Of the Pbs And Pbs-psii Complexesmentioning

confidence: 99%

“…strain PCC 7120 (Anabaena 7120, also known as Nostoc sp. PCC 7120) have a five cylinder core and eight peripheral rods with a molecular mass of ~6 000 kDa [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

“…A recent study demonstrated that CpcG3 is important for the association of a special PBS with PSI in Anabaena 7120 [39]. CpcG1, CpcG2, and CpcG4 of Anabaena 7120 are functionally similar to CpcG1 of Synechocystis 7002 and are responsible for the rod-core association [4,5].…”

Section: Interactions Between the Rods And The Corementioning

confidence: 99%

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Structural organization of an intact phycobilisome and its association with photosystem II

Chang¹,

et al. 2015

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Phycobilisomes (PBSs) are light-harvesting antennae that transfer energy to photosynthetic reaction centers in cyanobacteria and red algae. PBSs are supermolecular complexes composed of phycobiliproteins (PBPs) that bear chromophores for energy absorption and linker proteins. Although the structures of some individual components have been determined using crystallography, the three-dimensional structure of an entire PBS complex, which is critical for understanding the energy transfer mechanism, remains unknown. Here, we report the structures of an intact PBS and a PBS in complex with photosystem II (PSII) from Anabaena sp. strain PCC 7120 using single-particle electron microscopy in combination with biochemical and molecular analyses. In the PBS structure, all PBP trimers and the conserved linker protein domains were unambiguously located, and the global distribution of all chromophores was determined. We provide evidence that ApcE and ApcF are critical for the formation of a protrusion at the bottom of PBS, which plays an important role in mediating PBS interaction with PSII. Our results provide insights into the molecular architecture of an intact PBS at different assembly levels and provide the basis for understanding how the light energy absorbed by PBS is transferred to PSII.

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Section: Overall Structures Of the Pbs And Pbs-psii Complexesmentioning

confidence: 99%

“…strain PCC 7120 (Anabaena 7120, also known as Nostoc sp. PCC 7120) have a five cylinder core and eight peripheral rods with a molecular mass of ~6 000 kDa [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

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Structural organization of an intact phycobilisome and its association with photosystem II

Chang¹,

et al. 2015

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“…Four morphological types of PBS 1 are known: hemidiscoidal 7 , hemiellipsoidal 8 , block-type 9 and bundle-type 10 . The hemidiscoidal PBS contains a central core surrounded by peripheral rods 1, 11,12 . The chromophores in hemidiscoidal PBS are arranged in such a way that a photon absorbed by a chromophore in the peripheral rods is rapidly funnelled to chromophores in the core 13 and eventually to the terminal emitters (the core-membrane linker protein (L CM ) [14][15][16] or allophycocyanin D (ApcD) 17,18 ).…”

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confidence: 99%

Structure of phycobilisome from the red alga Griffithsia pacifica

Zhang

Liu

et al. 2017

Nature

204

199

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The cyanobacteria and red algae are two important groups of photosynthetic organisms that share a light-harvesting antenna known as the phycobilisome (PBS) [1][2][3][4] . PBSs are among the largest protein complexes in the living world and consist of phycobiliproteins (PBPs), including phycocyanin, phycoerythrin and allophycocyanin (APC), and linker proteins . Two subunits of PBPs, the α -and β -subunits, form an α β heterodimer that is conventionally called an (α β ) monomer. The monomer is then assembled into an (α β ) 3 trimer, the basic unit of PBS hierarchical assembly. The trimers of various PBPs are organized into a highly ordered supramolecular complex with the help of the linker proteins 1,5,6 . Four morphological types of PBS 1 are known: hemidiscoidal 7 , hemiellipsoidal 8 , block-type 9 and bundle-type 10. The hemidiscoidal PBS contains a central core surrounded by peripheral rods 1,11,12 . The chromophores in hemidiscoidal PBS are arranged in such a way that a photon absorbed by a chromophore in the peripheral rods is rapidly funnelled to chromophores in the core 13 and eventually to the terminal emitters (the core-membrane linker protein (L CM ) [14][15][16] or allophycocyanin D (ApcD) 17,18 ). The terminal emitters then transfer the energy to photosynthetic reaction centres 16,[19][20][21][22][23] . Currently, the mechanism of PBS assembly is poorly understood and the energy transfer routes within PBSs are not well defined. Although 3D structures of some individual PBPs have been reported (reviewed in refs 2, 3), the structures of most linker proteins are unknown and the complete structure of a PBS has not been published, to our knowledge. Here we report the cryo-electron microscopy (cryo-EM) structure of a PBS from the red alga Griffithsia pacifica at a resolution of 3.5 Å, which reveals details of the PBS architecture. Overall structureThe PBS from G. pacifica was purified and its intactness confirmed by its protein composition and spectroscopic features (Extended Data Fig. 1a-f). We reconstructed a 3D structure of the intact PBS by single particle cryo-EM with an overall resolution of 3.5 Å (Extended Data Table 1). Applying individual local masks improved the resolutions of local maps to 3.4-4.3 Å (Extended Data Fig. 2g). The PBS is one of the largest supramolecular complexes that has been reported, with a calculated molecular mass of approximately 16.8 megadaltons. The overall appearance is block-type 9 with twofold symmetry oriented perpendicularly to the thylakoid membranes (Fig. 1a-c and Extended Data Figs 1g-l, 3a-d). This PBS is larger than the hemiellipsoidal PBS isolated from Porphyridium cruentum8 and has dimensions of approximately 680 Å length, 390 Å height, and 450 Å thickness (Fig. 1a-c).The PBS contains a triangular core with the top cylinder B (formed by two APC trimers) sitting above two basal cylinders A and A′ (each formed by three APC trimers) surrounded by peripheral rods arranged in a staggered fashion (Fig. 1a-c and Extended Data Fig. 3c-e). In addition to the core and ...

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“…The authors hypothesized that this form of PC was a connector between rods and the core, but this assertion was based only on the fact that this form of PC copurifies with some AP, and stoichiometric competence for this assertion was not demonstrated. If this type of "connector" were to be required to attach rods onto cores, then the extensive electron microscopic analyses performed on isolated PBS would probably have revealed this extra rod segment, and demethyl-PC should have accounted for a major fraction of the total PC (41)(42)(43)(44)(45)(46)(47)(48)(49). We have also observed small amounts (ϳ1-3%) of unmethylated PC subunits in Synechococcus sp.…”

Section: Discussionmentioning

confidence: 99%

Biogenesis of Phycobiliproteins

Miller

Leonard

Pinsky

et al. 2008

Journal of Biological Chemistry

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All phycobiliproteins contain a conserved, post-translational modification on asparagine 72 of their ␤-subunits. Methylation of this Asn to produce ␥-N-methylasparagine has been shown to increase energy transfer efficiency within the phycobilisome and to prevent photoinhibition. We report here the biochemical characterization of the product of sll0487, which we have named cpcM, from the cyanobacterium Synechocystis sp. PCC 6803. Recombinant apo-phycocyanin and apo-allophycocyanin subunits were used as the substrates for assays with [methyl-3 H]Sadenosylmethionine and recombinant CpcM. CpcM methylated the ␤-subunits of phycobiliproteins (CpcB, ApcB, and ApcF) and did not methylate the corresponding ␣-subunits (CpcA, ApcA, and ApcD), although they are similar in primary and tertiary structure. CpcM preferentially methylated its CpcB substrate after chromophorylation had occurred at Cys 82 . CpcM exhibited lower activity on trimeric phycocyanin after complete chromophorylation and oligomerization had occurred. Based upon these in vitro studies, we conclude that this post-translational modification probably occurs after chromophorylation but before trimer assembly in vivo.

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Isolation, Characterization and Electron Microscopy Analysis of A Hemidiscoidal Phycobilisome Type from the Cyanobacterium Anabaena sp. PCC 7120

Cited by 66 publications

References 63 publications

Structural organization of an intact phycobilisome and its association with photosystem II

Structural organization of an intact phycobilisome and its association with photosystem II

Structure of phycobilisome from the red alga Griffithsia pacifica

Biogenesis of Phycobiliproteins

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