Photosynthetic proteins LHCII

The photosynthetic performance of the mutant does not change significantly under non-stress light conditions. However, the major LHCII isolated from this mutant appears less stable, as it dissociates more easily from the trimeric to the monomeric state and also into protein and unbound pigments (Tardy and Havaux, 1996). It may be this reduced amount and/or the reduced stability of trimeric LHCII in the aba mutant that is responsible for its reduced thylakoid stacking (Rock et al., 1992). 

Figure 7 Rogue s gaiiery of structures of peripherai antenna complexes. As labelled these include Chlorosomes from green sulfur bacteria, fused antenna domains of the Photosystem 1 core, the CP43 and CP47 proteins of Photosystem II, the Fenna-Matthew-Olson (FMO) protein associated with chlorosomes, LHI proteins surrounding a purple bacterial photosynthetic core, the peridinin-chlorophyll a protein of dinoflagellate algae, the LHCI and LHCII proteins found in plants and many algae, and the LHII protein complex that is associated with LHI in purple bacteria...

One important aspect of LHCII that specifically relates to other aspects discussed in the present review is the question of how the membrane environment (lipid composition, membrane curvature, etc.) affects the association of LHCII monomers to form trimers and the assembly of these trimers into the antenna complex around the photosynthetic reaction centers. The nonbilayer-forming lipid monogalactosyldiacylglycerol (MGDG) constitutes half of the thylakoid membrane. This membrane maintains its lamellar structure only with proteins inserted, predominantly LHCII which, due to its concave shape, eases the curvature pressure exerted by MGDG. It has been suggested that this curvature pressure is a driving force for protein interaction in the membrane [317] however, because it is not known whether, e.g., the formation of supercomplexes of LHCII trimers eases or increases curvature pressure, it is unclear whether MGDG (or other curvature... 

In photosynthetically active chloroplasts, the carotenoids are found as part of photosynthetic pigment-protein complexes (PPCs) in the thylakoid membranes. The core complex, CCI, contains one /3-carotene molecule per 40 chlorophyll a, whereas the light-harvesting complex LHCI is associated with lutein, violaxanthin, and neoxanthin. /3-Carotene is also located in CCII, ° while LHCII contains xanthophylls." The separation, identification, and nomenclature of the PPCs has been discussed in detail in several recent reviews. ... 

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