Freeze-Fractured Purple Membrane Particles: Protein Content

Fisher, Knute A.; Stoeckenius, Walther

doi:10.1126/science.867052

Cited by 82 publications

(31 citation statements)

References 25 publications

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“…It seems likely that any such detail is destroyed by plastic deformation during freeze-fracturing of thylakoids, although it is thought that this deformation is less extensive in membranes where complementarity between the EF and PF faces is preserved (14,22). Such fine structure has been reported for rotary shadowed particles of the PF face of the red blood cell membrane (26), but it is not clear to what extent it is caused by decoration, particularly under conditions of low shadow angle and a thin coating of platinum.…”

Section: Discussionmentioning

confidence: 99%

“…The molecular composition of light-harvesting complex particles has not been determined. However, a correlation between the size of freeze-fracture particles in the purple membrane of Halobacterium halobium and the electron diffraction map of this membrane has shown that each particle of 120 A diameter consists of several polypeptides, with a total molecular weight of about 300,000 (14). It is not valid to make a direct comparison between this membrane and light-harvesting complex liposomes since sufficient data are not yet available, but light-harvesting complex particles may contain about eight molecules of the light-harvesting chlorophyll a/b-protein, each of which contains approximately 14 molecules of chlorophyll (9).…”

Section: Discussionmentioning

confidence: 99%

“…Evidence from reconstitution (15,27,41) and specific labelling experiments (32) supports the idea that many freeze-fracture particles are composed of protein. Such particles are too large to consist of a single polypeptide, so it is probable that freeze-fracture particles consist of several polypeptides (14). There is an increasing amount of evidence in favour of the concept that the structural units visualised by freezefracturing consist of polypeptides organised into discrete functional units.…”

Section: Introductionmentioning

confidence: 99%

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Freeze-fracture studies on barley plastid membranes. III. Location of the light-harvesting chlorophyll-protein

Simpson

1979

Carlsberg Res. Commun.

137

112

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The thylakoids of chloroplasts from wild-type barley and the nuclear gene mutant chlorina-/2 were examined by freeze-fracturing and rotary shadowing. The advantages of rotary shadowing were: the shape of freeze-fracture particles was revealed, particles on membrane surfaces were seen in greater detail, estimation of particle density was more reliable, and measurements could be made of membrane ~hickness. When wild-type and chlorina-/2 thylakoid ultrastructure were compared, the most significant difference was the large reduction in the number of particles on the PFs face of the mutant. In addition, EFs particles were about 129/0 smaller in the mutant, whereas the appearance of the EFu, PFu and PSu was substantially the same as for wild-type thylakoids. These ultrastructural differences are correlated with the complete absence of the light-harvesting chlorophyll a/bprotein from chlorina-f2 thylakoids. Freeze-fracturing of purified light-harvesting complex in vesicles revealed particles similar in size and shape to those missing from the PFs face of chlorina-f2 but present on the PFs face of wild-type. It is concluded that in wild-type granal thylakoids, the light-harvesting chlorophyll a/b-protein is located in particles which are closely associated with EFs particles, but which cleave with the PFs face during freeze-fracturing.Abbreviations: EFs = endoplasmic fracture (stacked), EFu = endoplasmic fracture (unstacked), ES = endoplasmic surface, ESs = endoplasmic surface (stacked), ESu = endoplasmic surface (unstacked), PFs = protoplasmic fracture (stacked), PFu --protoplasmic fracture (unstacked), PSu = protoplasmic surface (unstacked), S.D. --standard deviation, S.E. = standard error of the mean, Tricine = N-(tris-(hydroxymethyl)-methyl)glycine.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Freeze-fracture studies on barley plastid membranes. III. Location of the light-harvesting chlorophyll-protein

Simpson

1979

Carlsberg Res. Commun.

137

112

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“…0105-1938/80/0045/0201/$ 02.00 useful to know the precise size of these freezefracture particles in order to calculate their molecular weight, and to correlate this with their polypeptide composition (see 6). Since most studies have employed uni-directionally shadowed replicas, it has only been possible to obtain an average value for particle size from their size distribution, and it has been assumed that these particles have a circular cross-section at the freeze-fracture plane (2).…”

Section: )mentioning

confidence: 99%

Freeze-fracture studies on barley plastid membranes IV. Analysis of freeze-fracture particle size and shape

Simpson

1980

Carlsberg Res. Commun.

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The shape and size of freeze-fracture particles of rotary shadowed barley thylakoids were measured and plotted as three-dimensional histograms. It was not possible to resolve discrete sub-populations of particles, distinct in shape or size, on any of the fracture faces examined. It is concluded that much of the variation in particle shape and size was due to plastic deformation during freeze-fracturing, and to shadowing artefacts. The suggestion is made that EFs particles are uniformly sized in vivo. Particle size measurements can be useful, however, in making comparisons between different fracture faces and between corresponding faces of wild-type and mutant membranes, as long as the limitations of the technique are considered. The differences between corresponding faces of wild-type and chlorina-f2 thylakoids were found to be statistically significant for the EFs, ESs and PF faces.

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“…' Although it has been assumed that the lymphocyte IMP are mainly proteins that span the membrane (3, 4), it may well be that the large majority of lymphocyte transmembrane proteins are not revealed as IMP by the freeze-fracture technique, possibly because they do not form molecular aggregates of large enough size (9) .…”

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confidence: 99%

Intramembrane particles and the organization of lymphocyte membrane proteins

Kuby¹,

Wofsy²

1981

The Journal of Cell Biology

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An experimental system was developed in which the majority of all lymphocyte cell-surface proteins, regardless of antigenic specificity, could be cross-linked and redistributed in the membrane to determine whether this would induce a corresponding redistribution of intramembrane particles (IMP) . Mouse spleen cells were treated with p-diazoniumphenyl-ß-D-lactoside (lac) to modify all exposed cell-surface proteins . Extensive azo-coupling was achieved without significantly reducing cell viability or compromising cellular function in mitogen-or antigen-stimulated cultures . When the Lac-modified cell-surface proteins were capped with a sandwich of rabbit antilactoside antibody and fluorescein-goat anti-rabbit Ig, freeze-fracture preparations obtained from these cells revealed no obvious redistribution of IMP on the majority of fracture faces. However, detailed analysis showed a statistically significant 35% decrease (P < 0.01) in average IMP density in the E face of the lac-capped spleen cells compared with control cells, whereas a few E-face micrographs showed intense IMP aggregation . In contrast, there was no significant alteration of P-face IMP densities or distribution . Apparently, the majority of E-face IMP and virtually all P-face IMP do not present accessible antigenic sites on the lymphocyte surface and do not associate in a stable manner with surface protein antigens . This finding suggests that IMP, as observed in freeze-fracture analysis, may not comprise a representative reflection of lymphocyte transmembrane protein molecules and complexes because other evidence establishes : (a) that at least some common lymphocyte surface antigens are indeed exposed portions of transmembrane proteins and (b) that the aggregation of molecules of any surface antigen results in altered organization of contractile proteins at the cytoplasmic face of the membrane .The role of the plasma membrane in the transmission of information can be seen in a number of systems where cells have been shown to be activated by an event at the cell membrane leading to proliferation and/or differentiation (5,8,23,26). Although the mechanism of lymphocyte activation is not known, there is evidence to suggest that the binding of insolubilized antigen or mitogen to membrane receptors may, under some conditions, be sufficient to initiate the cellular activation process (8) .There is considerable evidence for an association between lymphocyte cell-surface proteins and an underlying actinmyosin contractile system (2, 10, 15), which may be critically involved in the transmission of signals to or from the cell interior. However, the role of intramembrane particles (IMP) in this interaction remains unresolved. In erythrocytes, experiments have suggested an interaction of IMP with the underlying peripheral protein, spectrin, as well as with erythrocyte surface proteins (24). In the lymphocyte membrane, associa-THE JOURNAL Of CELL BIOLOGY " VOLUME 88 MARCH 1981 591-598 ©The Rockefeller University Press " 0021-9525/81/03/0591/08 $1 .00 tion...

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Freeze-Fractured Purple Membrane Particles: Protein Content

Cited by 82 publications

References 25 publications

Freeze-fracture studies on barley plastid membranes. III. Location of the light-harvesting chlorophyll-protein

Freeze-fracture studies on barley plastid membranes. III. Location of the light-harvesting chlorophyll-protein

Freeze-fracture studies on barley plastid membranes IV. Analysis of freeze-fracture particle size and shape

Intramembrane particles and the organization of lymphocyte membrane proteins

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