Reconstitution of chlorophyll a/b light-harvesting complexes: Xanthophyll-dependent assembly and energy transfer

Fg, Plumley; Gw, Schmidt

doi:10.1073/pnas.84.1.146

Cited by 326 publications

(208 citation statements)

References 28 publications

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“…It also provides an assay system for examining the mechanisms by which LHCP becomes associated with its molecular neighbors in the thylakoid membranes. Until now, such studies were restricted either to the more complex situation where pLHCP is first imported into intact chloroplasts and subsequently assembled or to reconstitution procedures (10,24) that are clearly dissimilar from the in vivo process.…”

Section: Discussionmentioning

confidence: 99%

Light-Harvesting Chlorophyll a/b Protein

Cline¹

1988

Plant Physiol.

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The apoprotein of the light-harvesting chlorophyll alb protein (LHCP) is a major integral thylakoid membrane protein that is normally complexed with chlorophyll and xanthophylls and serves as the antenna complex of photosystem IL LHCP is encoded in the nucleus and synthesized in the cytosol as a higher molecular weight precursor that is subsequently imported into chloroplasts and assembled into thylakoids. In a previous study it was established that the LHCP precursor can integrate into isolated thylakoid membranes. The present study demonstrates that under conditions designed to preserve thylakoid structure, the inserted LHCP precursor is processed to mature size, assembled into the LHC II chlorophyll-protein complex, and localized to the appressed thylakoid membranes. Under these conditions, light can partially replace exogenous ATP in the membrane integration process.Thylakoid membranes contain approximately 45 different polypeptides, most of which are organized into four distinct supramolecular complexes: PSI, PSII, Cyt b/f, and the ATP synthase (11,23). In most plant chloroplasts, these complexes are nonuniformly distributed into two different structural thylakoid domains, the appressed membranes and the nonappressed membranes. PSII complexes are located predominantly in the appressed membranes, PSI and ATP synthase are located exclusively in the nonappressed membranes, and the Cyt blf complex appears to be present in both domains (23).Biogenesis of thylakoid protein complexes is an intriguing but little understood process. Each complex contains nuclearly encoded as well as chloroplast-encoded polypeptides (11). Thus, complex formation involves coordinate assembly of polypeptides that derive from two different cellular compartments. Chloroplast-encoded polypeptides are synthesized at or near their functional locations on thylakoid-bound ribosomes (21). Conversely, nuclearly encoded polypeptides must be imported from their site of synthesis in the cytosol (29). The fact that thylakoids are spatially separated from the delimiting envelope membranes indicates that assembly of these polypeptides is a multistep process, involving interaction with three different membranes. The assembly pathway for cytosolically synthesized thylakoid proteins has not been definitively established. However, recent studies (9, 30) suggest that these proteins are translocated across the envelope into the aqueous stromal matrix, where they are assembled into thylakoids by a second protein translocation/integration process.

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Section: Discussionmentioning

confidence: 99%

Light-Harvesting Chlorophyll a/b Protein

Cline¹

1988

Plant Physiol.

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“…Nevertheless, individual complexes show different biochemical and spectroscopic properties (see e.g., (Pascal et al 1999)), mainly due to the fact that the pigment composition is not identical (Sandona et al 1998). Mutations of the putative Chl-binding residues followed by in vitro reconstitution (Plumley and Schmidt 1987) has allowed the characterization of the chromophores in most binding sites Remelli et al 1999;Yang et al 1999;Rogl and Kuhlbrandt 1999;Ballottari et al 2009;Passarini et al 2009). The four Chl-binding sites in the center (602, 603, 610 and 612) accommodate Chls a in all antenna complexes.…”

Section: Outer Antenna Complexesmentioning

confidence: 99%

Light-Harvesting in Photosystem II

Amerongen¹,

Dekker

2003

Light-Harvesting Antennas in Photosynthesis

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Water oxidation in photosynthesis takes place in photosystem II (PSII). This photosystem is built around a reaction center (RC) where sunlight-induced charge separation occurs. This RC consists of various polypeptides that bind only a few chromophores or pigments, next to several other cofactors. It can handle far more photons than the ones absorbed by its own pigments and therefore, additional excitations are provided by the surrounding light-harvesting complexes or antennae. The RC is located in the PSII core that also contains the inner light-harvesting complexes CP43 and CP47, harboring 13 and 16 chlorophyll pigments, respectively. The core is surrounded by outer light-harvesting complexes (Lhcs), together forming the so-called supercomplexes, at least in plants. These PSII supercomplexes are complemented by some ''extra'' Lhcs, but their exact location in the thylakoid membrane is unknown. The whole system consists of many subunits and appears to be modular, i.e., both its composition and organization depend on environmental conditions, especially on the quality and intensity of the light. In this review, we will provide a short overview of the relation between the structure and organization of pigment-protein complexes in PSII, ranging from individual complexes to entire membranes and experimental and theoretical results on excitation energy transfer and charge separation. It will become clear that time-resolved fluorescence data can provide invaluable information about the organization and functioning of thylakoid membranes. At the end, an overview will be given of unanswered questions that should be addressed in the near future.

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“…This prosthetic group is linked to K216 of helix G via a protonated Schiff base. From a biophysical point of view, BR is important not only because of its intriguing photocycle [40,41], but also because it is one of only a handful of membrane proteins that can be folded in vitro [42][43][44][45][46][47][48].…”

mentioning

confidence: 99%