Les membranes photosynthétiques des algues à biliproteines observées apres cryodécapage

Lefort‐Tran, M.; Cohen-Bazire, Germaine; Pouphile, M.

doi:10.1016/s0022-5320(73)80056-5

Cited by 44 publications

(13 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition, freezefracture of thylakoid membranes of several (but not all [134])PBsomecontaining organisms has shown parallel rows of particles, the spacing between which closely follows the spacing between PBsome rows [92, 111 ; see also 36,134]. These data supported the hypothesis that the aligned exoplasmic fracture face (EF) particles were PS II particles and were in direct contact with PBsomes [85]. Later observations of organisms deficient in some photosynthetic function (e.g., heterocysts which lack PS II [44] or mutants without PBsomes [149]) and comparison of these with the ultrastructure of vegetative or wild-type cells provided further evidence for this hypothesis.…”

Section: F:ttrastructural Studies Ofphycobilisome Photosystem H Assmentioning

confidence: 71%

Phycobilisome structure and function

1986

View full text Add to dashboard Cite

Phycobilisomes are aggregates of light-harvesting proteins attached to the stroma side of the thylakoid membranes of the cyanobacteria (blue-green algae) and red algae. The water-soluble phycobiliproteins, of which there are three major groups, tetrapyrrole chromophores covalently bound to apoprotein. Several additional protiens are found within the phycobilisome and serve to link the phycobiliproteins to each other in an ordered fashion and also to attach the phycobilisome to the thylakoid membrane. Excitation energy absorbed by phycoerythrin is transferred through phycocyanin to allophycocyanin with an efficiency approximating 100%. This pathway of excitation energy transfer, directly confirmed by time-resolved spectroscopic measurements, has been incorporated into models describing the ultrastructure of the phycobilisome. The model for the most typical type of phycobilisome describes an allophycocyanin-containing core composed of three cylinders arranged so that their longitudinal axes are parallel and their ends form a triangle. Attached to this core are six rod structures which contain phycocyanin proximal to the core and phycoerythrin distal to the core. The axes of these rods are perpendicular to the longitudinal axis of the core. This arrangement ensures a very efficient transfer of energy. The association of phycoerythrin and phycocyanin within the rods and the attachment of the rods to the core and the core to the thylakoid require the presence of several 'linker' polypeptides. It is recently possible to assemble functionally and structurally intact phycobilisomes in vitro from separated components as well as to reassociate phycobilisomes with stripped thylakoids. Understanding of the biosynthesis and in vivo assembly of phycobilisomes will be greatly aided by the current advances in molecular genetics, as exemplified by recent identification of several genes encoding phycobilisome components.Combined ultrastructural, biochemical and biophysical approaches to the study of cyanobacterial and red algal cells and isolated phycobilisome-thylakoid fractions are leading to a clearer understanding of the phycobilisome-thylakoid structural interactions, energy transfer to the reaction centers and regulation of excitation energy distribution. However, compared to our current knowledge concerning the structural and functional organization of the isolated phycobilisome, this research area is relatively unexplored.

show abstract

Section: F:ttrastructural Studies Ofphycobilisome Photosystem H Assmentioning

confidence: 71%

Phycobilisome structure and function

1986

View full text Add to dashboard Cite

show abstract

“…Based on energy transfer characteristics in vivo (10,(20)(21)(22)(23)(24)(25), freeze-fracture studies of putative PSII particles (19,36,38), and the isolation of functionally coupled PBsome-PSII preparations (5), it is believed that PSII and PBsomes are functionally and structurally associated. Thus, the distribution of PSII in the thylakoid membrane may be defined by the arrangement of the PBsomes.…”

Section: Arrangement and Interaction Of Phycobilisomes And Photosystemsmentioning

confidence: 99%

Growth under Red Light Enhances Photosystem II Relative to Photosystem I and Phycobilisomes in the Red Alga Porphyridium cruentum

Cunningham¹,

Dennenberg²,

Jursinic³

et al. 1990

Plant Physiol.

View full text Add to dashboard Cite

Acclimation of the photosynthetic apparatus to light absorbed primarily by photosystem I (PSI) or by photosystem 11 (PSII) was studied in the unicellular red alga Porphyridium cruentum (ATCC 50161). Cultures grown under green light of 15 microeinsteins per square meter per second (PSII light; absorbed predominantly by the phycobilisomes) exhibited a PSII/PSI ratio of 0.26 ± 0.05. Under red light (PSI light; absorbed primarily by chlorophyll) of comparable quantum flux, cells contained nearly five times as many PSII per PSI (1.21 ± 0.10), and three times as many PSII per cell. About 12% of the chlorophyll was attributed to PSII in green light, 22% in white light, and 39% in red light-grown cultures. Chlorophyll antenna sizes appeared to remain constant at about 75 chlorophyll per PSII and 140 per PSI. Spectral quality had little effect on cell content or composition of the phycobilisomes, thus the number of PSII per phycobilisome was substantially greater in red light-grown cultures (4.2 ± 0.6) than in those grown under green (1.6 ± 0.3) or white light (2.9 ± 0.1). Total photosystems (PSI + PSII) per phycobilisome remained at about eight in each case. Carotenoid content and composition was little affected by the spectral composition of the growth light. Zeaxanthin comprised more than 50% (mole/mole), ,8-carotene about 40%, and cryptoxanthin about 4% of the carotenoid pigment. Despite marked changes in the light-harvesting apparatus, red and green light-grown cultures have generation times equal to that of cultures grown under white light of only one-third the quantum flux.

show abstract

“…In PBsome-containing organisms it is generally assumed that the arrangement of the photosystems in the thylakoid is predictable from the PSII/phycobiliprotein ratio (6,7) and that the PBsome distribution on the stromal surface is indicative of the PSII location (8,9). Since PBsomes with PSII activity have been isolated, a direct functional association exists in vivo (10), although a direct interaction between PBsomes and PSI cannot be ruled out.…”

mentioning

confidence: 99%

Photosynthetic membrane topography: quantitative in situ localization of photosystems I and II.

Mustárdy

Cunningham

Gantt

1992

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

View full text Add to dashboard Cite

Photosynthesis is a biological process whose efficiency depends on the coordinated interaction of several participating protein complexes that reside in the photosynthetic membrane. Our understanding of the photosynthetic membrane structure is largely derived from studies on fractionated membranes and from conventional electron microscopy (1, 2), and our knowledge of the spatial and functional interaction between principal membrane complexes is quite limited. Such information is directly relevant to excitation energy transfer as well as to the diffusion of mobile electron carriers (3, 4) in photosynthetic membranes of oxygen-evolving plants. Major integral protein complexes include ATP synthase, cytochrome b6/f, photosystem I (PSI), and photosystem II (PSII) and LHCII in green plants. In phycobilisome (PBsome)-containing organisms-namely, red algae and cyanobacteria-the LHCII complex appears to be absent and PBsomes on the stromal surface serve as the principal light-harvesting antennae (5). In PBsome-containing organisms it is generally assumed that the arrangement of the photosystems in the thylakoid is predictable from the PSII/phycobiliprotein ratio (6, 7) and that the PBsome distribution on the stromal surface is indicative of the PSII location (8, 9). Since PBsomes with PSII activity have been isolated, a direct functional association exists in vivo (10), although a direct interaction between PBsomes and PSI cannot be ruled out. The following questions are being addressed here: (i) how many PSI and PSII centers exist per unit of surface area, (ii) is the distribution of PSI and PSII uniform throughout the membrane, (iii) are the photosystems present as monomers or as clusters, and (iv) if they are clustered, does the cluster size change under different growth conditions?By conventional immunocytochemical methods, the subcellular distribution of proteins in plants is well established, including specific localization of a number of chloroplast components in land plants and algae (1,11,12). We have shown that this approach can be used to provide a quantitative measure of the relative amounts of PSI and PSII in Porphyridium cruentum (13,14). However, since antigenic sites are accessible only on exposed surfaces of embedded sections, the absolute number of particular components is greatly underestimated, and spatial distances between individual complexes are difficult to ascertain.To ascertain the spatial relationships of PSI and PSII requires intact membranes and a means of identifying the photosystems. By freeze-fracture, 10-nm particles exposed on the exoplasmic fracture face are regarded as representing PSII centers. The isolation of PSII particles and their visualization in lipid vesicles support this attribution (15). Also, there is good evidence that some 10-to 13-nm particles on the protoplasmic fracture face represent PSI (2), but one cannot identify individual particles as photosystems. Since PSI and PSII particles are not identifiable in the same fracture-face, meaningful spatial correlations...

show abstract

Les membranes photosynthétiques des algues à biliproteines observées apres cryodécapage

Cited by 44 publications

References 19 publications

Phycobilisome structure and function

Phycobilisome structure and function

Growth under Red Light Enhances Photosystem II Relative to Photosystem I and Phycobilisomes in the Red Alga Porphyridium cruentum

Photosynthetic membrane topography: quantitative in situ localization of photosystems I and II.

Contact Info

Product

Resources

About