Structure of the Phycobilisome Antennae in Cyanobacteria and Red Algae

Adir, Noam

doi:10.1002/9783527623464.ch11

Cited by 19 publications

(15 citation statements)

References 120 publications

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“…The core of the PBS is made up of two to five cylinders (Fig. S1), each composed of four (αβ) 3 trimers of allophycocyanin (APC) (22,23). Two basal core cylinders sit on top of the membrane, and contain the main form of APC (APC 660 ) and one copy each of three minor APC forms, ApcF (a β-like subunit) and ApcD and ApcE (α-like subunits; ApcE is also known as L CM , and in addition to the chromophore-bearing domain also contains large linker domains of unknown position) (Fig.…”

Section: Significancementioning

confidence: 99%

Orange carotenoid protein burrows into the phycobilisome to provide photoprotection

Harris

Tal

Jallet

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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In cyanobacteria, photoprotection from overexcitation of photochemical centers can be obtained by excitation energy dissipation at the level of the phycobilisome (PBS), the cyanobacterial antenna, induced by the orange carotenoid protein (OCP). A single photoactivated OCP bound to the core of the PBS affords almost total energy dissipation. The precise mechanism of OCP energy dissipation is yet to be fully determined, and one question is how the carotenoid can approach any core phycocyanobilin chromophore at a distance that can promote efficient energy quenching. We have performed intersubunit cross-linking using glutaraldehyde of the OCP and PBS followed by liquid chromatography coupled to tandem mass spectrometry (LC/MS-MS) to identify cross-linked residues. The only residues of the OCP that cross-link with the PBS are situated in the linker region, between the N-and C-terminal domains and a single C-terminal residue. These links have enabled us to construct a model of the site of OCP binding that differs from previous models. We suggest that the N-terminal domain of the OCP burrows tightly into the PBS while leaving the OCP C-terminal domain on the exterior of the complex. Further analysis shows that the position of the small core linker protein ApcC is shifted within the cylinder cavity, serving to stabilize the interaction between the OCP and the PBS. This is confirmed by a ΔApcC mutant. Penetration of the N-terminal domain can bring the OCP carotenoid to within 5-10 Å of core chromophores; however, alteration of the core structure may be the actual source of energy dissipation.photosynthesis | light harvesting | nonphotochemical quenching | cyanobacteria | cross-linking E xcess energy arriving at photochemical reaction centers (RCs) can be detrimental (1, 2), leading to loss of photosynthetic viability (photoinhibition; PI) (3, 4). Cyanobacteria have evolved several mechanisms for energy dissipation to deal with overexcitation (5, 6). The major light-harvesting complex (LHC) in cyanobacteria is the phycobilisome (PBS), a giant complex that can functionally transfer energy to two to four RCs (7-9). If overexcitation occurs rapidly, photoprotection can be achieved by decreasing the energy arriving at the RCs by increasing energy thermal dissipation (nonphotochemical quenching; NPQ) or by physical (or functional) disconnection of the PBS (10, 11). In most cyanobacterial species, NPQ is obtained by the presence a 35-kDa, water-soluble, orange carotenoid protein (OCP) (12, 13). OCP-dependent NPQ was shown to be induced (14, 15) by strong blue-green light. The OCP has two states-an inactive resting orange state (OCP O ) and an active red state (OCP R ). Upon illumination, the OCP undergoes carotenoid and protein conformational changes to yield the metastable OCP R (16). The OCP R binds to the PBS and significantly quenches excitation energy and PBS fluorescence (17). The OCP noncovalently binds a single keto-carotenoid chromophore, 3′-hydroxyechinenone (hECN). The high-resolution crystal structure of the OCP O [...

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Section: Significancementioning

confidence: 99%

Orange carotenoid protein burrows into the phycobilisome to provide photoprotection

Harris

Tal

Jallet

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…The phycobilisome (PBS) is an enormous (3)(4)(5)(6)(7) light-harvesting complex made up of pigmented phycobiliproteins (PBPs) and mostly unpigmented proteins (collectively termed linker proteins) that are arranged in two highly organized subcomplexes: six to eight rods surrounding a core of two to five cylinders. [1][2][3][4][5] Models of the specific arrangement of the rods surrounding the core to form the overall PBS architecture have been suggested on the basis of electron microscopy of isolated PBS particles, stabilized in high-ionic-strength phosphate buffer.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3][4][5] Models of the specific arrangement of the rods surrounding the core to form the overall PBS architecture have been suggested on the basis of electron microscopy of isolated PBS particles, stabilized in high-ionic-strength phosphate buffer. It is clear that the direction of energy transfer correlates with the position of the pigment within the complex.…”

Section: Introductionmentioning

confidence: 99%

High-Resolution Crystal Structures of Trimeric and Rod Phycocyanin

David

Marx

Adir

2011

Journal of Molecular Biology

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“…The most accepted structural model of the entire PBS shows the rods radiating of the central core substructure (6,8,18). This proposed structure is based on electron microscopy analysis of single PBS complexes and leaves two open questions: (i) What is the method of attachment of the PBS subcomponents, the rods and core?…”

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Investigation of Phycobilisome Subunit Interaction Interfaces by Coupled Cross-linking and Mass Spectrometry

Tal

Trabelcy

Gerchman

et al. 2014

Journal of Biological Chemistry

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Background:The phycobilisome is assembled from many subunits, but the entire structure has not been determined. Results: Coupled cross-linking/MS revealed neighboring residues within the interfaces between subunits. Conclusion: The rods completely cover the core cylinders and are not in a staggered assembly form. Significance: Energy transfer from rods to cores overcomes a jump of over 30 Å without loss of efficiency.

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Structure of the Phycobilisome Antennae in Cyanobacteria and Red Algae

Cited by 19 publications

References 120 publications

Orange carotenoid protein burrows into the phycobilisome to provide photoprotection

Orange carotenoid protein burrows into the phycobilisome to provide photoprotection

High-Resolution Crystal Structures of Trimeric and Rod Phycocyanin

Investigation of Phycobilisome Subunit Interaction Interfaces by Coupled Cross-linking and Mass Spectrometry

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