The light-harvesting chlorpohyll-protein complex of photosystem II. Its location in the photosynthetic membrane.

Abstract

We have investigated the structure of the photosynthetic membrane in a mutant of barley known to lack a chlorophyll-binding protein. This protein is thought to channel excitation energy to photosystem II, and is known as the "light-harvesting chlorophyll-protein complex." Extensive stacking of thylakoids into grana occurs in both mutant and wild-type chloroplasts. Examination of membrane internal structure by freeze-fracturing indicates that only slight differences exist between the fracture faces of mutant and wild-type membranes. These differences are slight reductions in the size of particles visible on the EFs fracture face, and in the number of particles seen on the PFs fracture face. No differences can be detected between mutant and wild-type on the etched outer surface of the membrane. In contrast, tetrameric particles visible on the etched inner surface of wild-type thylakoids are extremely difficult to recognize on similar surfaces of the mutant. These particles can be recognized on inner surfaces of the mutant membranes when they are organized into regular lattices, but these lattices show a much closer particle-to-particle spacing than similar lattices in wild-type membranes.Although several interpretations of these data are possible, these observations are consistent with the proposal that the light-harvesting chlorophyll-protein complex of photosystem II is bound to the tetramer (which is visible on the EFs face as a single particle) near the inner surface of the membrane. The large tetramer, which other studies have shown to span the thylakoid membrane, may represent an assembly of protein, lipid, and pigment comprising all the elements of the photosystem II reaction. A scheme is presented which illustrates one possibility for the integration of the light reaction across the photosynthetic membrane.The light reaction of photosynthesis is localized within the thylakoid membranes found in higher plants and green algae. The structure of these membranes is exceedingly complex, but now seems to be understood in general terms. At least two types of particles exist within the membrane, and can be visualized by the freeze-fracture technique (10,14,22). The larger of these particles is found principally in stacked (grana) regions of the chloroplast (14, 33, footnote 1), spans the thylaStaehelin, L. A. 1976. Reversible particle movements associated with unstacking and restacking of chloroplast membranes in vitro.

Extrinsic polypeptides of the chloroplast oxygen evolving complex constitute the tetrameric ESs particles of higher plant thylakoids

“…Indirect evidence, based on the loss of EFs particles in photosystem II mutants (15,23), further indicated that EFs panicles contain the reaction centre ofphotosystem II. Examination of a barley mutant lacking Chl b and LHCII, in which the EFs particles were reduced in size, led to the suggestion that EFs particles normally contain LHCII, the major light-harvesting chlorophyll-protein of thylakoids (16). This model was extended by AR-MOND et al (6), who followed the greening of pea grown under intermittent light and then transferred to continuous light.…”

“…Their model indicates that LHCII extends into the thylakoid lumen and presumably forms part of the 4 subunits of the tetrameric ESs particle. The Chl b-less barley mutant contains tetrameric ESs panicles (16,22), but they are significantly smaller than those of wild type thylakoids. A re-examination of this mutant led to the proposal that LHCII is located in PFs particles, and that the reduction in EFs and ESs particle size was postulated to be due to the loss of other Chl a/b-binding proteins (22).…”

Photoprotective Energy Dissipation Involves the Reorganization of Photosystem II Light-Harvesting Complexes in the Grana Membranes of Spinach Chloroplasts

“…The complementary protoplasmic fracture face of the stacked membranes (PFs) contains the ;8-nm LHCII particles (Miller et al, 1976;Simpson, 1979). The protoplasmic fracture face of the unstacked membranes is distinguished on the basis of its slightly larger asymmetric ;10-nm photosystem I particles (Simpson, 1982).…”

“…These supercomplexes represent the basic functional units of the PSII-LHCII macrostructure and can be supplemented by an additional three to four loosely attached LHCII trimers (L-trimers) Dekker et al, 1999). These C 2 S 2 and C 2 S 2 M 2 PSII-LHCII supercomplexes can also further become arranged into higher-order semicrystalline arrays (Miller et al, 1976;Staehelin, 1976;Boekema et al, 2000;Kirchhoff et al, 2007a;Daum et al, 2010). In contrast with PSII, photosystem I and the ATP synthase complex are mainly confined to the nonappressed stromal lamellae regions of the thylakoid membrane and the grana end membranes (reviewed in Hankamer et al, 1997;Dekker and Boekema, 2005;Daum et al, 2010).…”

Cytochemical study of diaminobenzidine oxidation by isolated Vicia chloroplasts under illumination.

“…Recently, the freeze fracture technique has been introduced to the study of the particulate structure of the thylakoid membrane (1,2,4,17,23,24). The small particles, presumably the PS-I complexes, are embedded in the thylakoid membrane in a manner that they are localized more externally to protrude partially into the partition side, that is, the outer surface side (1, 2, 4, 17), or to have a wider frontage on this side (23,24).…”