Chlorophyll-proteins of the photosystem II antenna system. J Biol Chem

Dipartimento di Biologia, Università di Padova, Italy.
Journal of Biological Chemistry (Impact Factor: 4.57). 10/1987; 262(27):13333-41.
Source: PubMed


The chlorophyll-protein complexes of purified maize photosystem II membranes were separated by a new mild gel electrophoresis system under conditions which maintained all of the major chlorophyll a/b-protein complex (LHCII) in the oligomeric form. This enabled the resolution of three chlorophyll a/b-proteins in the 26-31-kDa region which are normally obscured by monomeric LHCII. All chlorophyll a/b-proteins had unique polypeptide compositions and characteristic spectral properties. One of them (CP26) has not previously been described, and another (CP24) appeared to be identical to the connecting antenna of photosystem I (LHCI-680). Both CP24 and CP29 from maize had at least one epitope in common with the light-harvesting antennae of photosystem I, as shown by cross-reactivity with a monoclonal antibody raised against LHCI from barley thylakoids. A complex designated Chla.P2, which was capable of electron transport from diphenylcarbazide to 2,6-dichlorophenolindophenol, was isolated by nondenaturing gel electrophoresis. It lacked CP43, which therefore can be excluded as an essential component of the photosystem II reaction center core. Fractionation of octyl glucoside-solubilized photosystem II membranes in the presence and absence of Mg2+ enabled the isolation of the Chla . P2 complex and revealed the existence of a light-harvesting complex consisting of CP29, CP26, and CP24. This complex and the major light-harvesting system (LHCII) are postulated to transfer excitation energy independently to the photosystem II reaction center via CP43.

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    • "Furthermore, Boekema et al. [13] proposed that the very structure of the PSII supercomplex is important for NPQ formation. The structure of the PSII supercomplex is referred to as C 2 S 2 M 2 and is composed of C 2 , two RCII core complexes, and two strongly (S 2 ) and two moderately (M 2 ) bound LHCII trimers, as well as three minor antenna proteins [7] [13] [56] [32] [24]. However, recently we managed to grow plants largely devoid of RCII that were still capable of forming NPQ that was almost two times larger than that of the untreated plants [8] [10]. "
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    ABSTRACT: Plants with varying levels of PsbS protein were grown on lincomycin. Enhanced levels of non-photochemical fluorescence quenching (NPQ) in over-expressers of the protein have been observed. This was accompanied by increased amplitude of the irreversible NPQ component, qI, previously considered to reflect mainly photoinhibition of PSII reaction centres (RCII). However, since RCIIs were largely absent the observed qI is likely to originate from the LHCII antenna. In chloroplasts of over-expressers of PsbS grown on lincomycin an abnormally large NPQ (∼7) was characterised by a 0.34ns average chlorophyll fluorescence lifetime. Yet the lifetime in the Fm state was similar to that of wild-type plants. 77K fluorescence emission spectra revealed a specific 700nm peak typical of LHCII aggregates as well as quenching of the PSI fluorescence at 730nm. The aggregated state manifested itself as a clear change in the distance between LHCII complexes detected by freeze-fracture electron microscopy. Grana thylakoids in the quenched state revealed 3 times more aggregated LHCII particles compared to the dark-adapted state. Overall, the results directly demonstrate the importance of LHCII aggregation in the NPQ mechanism and show that the PSII supercomplex structure plays no role in formation of the observed quenching. Copyright © 2015 Elsevier B.V. All rights reserved.
    Full-text · Article · Jul 2015 · Journal of photochemistry and photobiology. B, Biology
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    • "PSII is a multi-subunit protein located in the thylakoid membrane. Each subunit is composed of a dimeric core complex (RCII) of specialised chlorophyll a molecules (P680), two strongly bound LHCII and two moderately bound LHCII; therefore, it is often referred to as the C2S2M2 supercomplex (Bassi et al. 1987; Boekema et al. 1995, 1998; Yakushevska et al. 2003). There are six Lhcb polypeptides in PSII (Boekema et al. 1995; Kouřil et al. 2012). "
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    ABSTRACT: Arabidopsis plants grown at low light were exposed to a gradually increasing actinic light routine. This method allows for the discerning of the photoprotective component of NPQ, pNPQ and photoinhibition. They exhibited lower values of Photosystem II (PSII) yield in comparison to high-light grown plants, and higher calculated dark fluorescence level (F′o calc.) than the measured one (F′o act.). As a result, in low-light grown plants, the values of qP measured in the dark appeared higher than 1. Normally, F′o act. and F′o calc. match well at moderate light intensities but F′o act. becomes higher at increasing intensities due to reaction centre (RCII) damage; this indicates the onset of photoinhibition. To explain the unusual increase of qP in the dark in low-light grown plants, we have undertaken an analysis of PSII antenna size using biochemical and spectroscopic approaches. Sucrose gradient separation of thylakoid membrane complexes and fast fluorescence induction experiments illustrated that the relative PSII cross section does not increase appreciably with the rise in PSII antenna size in the low-light grown plants. This suggests that part of the increased LHCII antenna is less efficiently coupled to the RCII. A model based upon the existence of an uncoupled population LHCII is proposed to explain the discrepancies in calculated and measured values of F′o.
    Full-text · Article · Feb 2015 · Photosynthesis Research
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    • "High light exposure can lead to photodamage in the crucial but vulnerable component of the photosynthetic machinery, the photosystem II (PSII) reaction centre (RCII) (Powles, 1984; Aro et al., 1993b; Barber, 1995). PSII is composed of major light-harvesting complex II (LHCII) and minor (CP24, CP26, and CP29) light-harvesting antenna proteins, core antenna complexes (CP43 and CP47), and the RCII core complex (Bassi et al., 1987; Boekema et al., 1995; Andersson et al., 2001; Dekker and Boekema, 2003; Yakushevska et al., 2003). Responsible for the generation of electrons that initiate the photosynthetic electron transport reactions and evolution of oxygen, PSII is fundamental to all life on our planet (Melis, 1999; Barber, 2002, 2009; Umena et al., 2011). "
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    ABSTRACT: The efficiency of protective energy dissipation by non-photochemical quenching (NPQ) in photosystem II (PSII) has been recently quantified by a new non-invasive photochemical quenching parameter, qPd. PSII yield (ФPSII) was expressed in terms of NPQ, and the extent of damage to the reaction centres (RCIIs) was calculated via qPd as: ФPSII=qPd×(F v/F m)/{1+[1-(F v/F m)]×NPQ}. Here this approach was used to determine the amount of NPQ required to protect all PSII reaction centres (pNPQ) under a gradually increasing light intensity, in the zeaxanthin-deficient (npq1) Arabidopsis mutant, compared with PsbS protein-deficient (npq4) and wild-type plants. The relationship between maximum pNPQ and tolerated light intensity for all plant genotypes followed similar trends. These results suggest that under a gradually increasing light intensity, where pNPQ is allowed to develop, it is only the amplitude of pNPQ which is the determining factor for protection. However, the use of a sudden constant high light exposure routine revealed that the presence of PsbS, not zeaxanthin, offered better protection for PSII. This was attributed to a slower development of pNPQ in plants lacking PsbS in comparison with plants that lacked zeaxanthin. This research adds further support to the value of pNPQ and qPd as effective parameters for assessing NPQ effectiveness in different types of plants. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology.
    Full-text · Article · Nov 2014 · Journal of Experimental Botany
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