scholarly journals Composition and Function of Thylakoid Membranes from Grana-rich and Grana-deficient Chloroplast Mutants of Barley

1979 ◽  
Vol 63 (1) ◽  
pp. 174-182 ◽  
Author(s):  
Niels C. Nielsen ◽  
Robert M. Smillie ◽  
K. W. Henningsen ◽  
Diter Von Wettstein ◽  
C. S. French
Keyword(s):  
Thylakoid Membranes ◽  
Chloroplast Mutants ◽  
And Function

The structure and function of grana-free thylakoid membranes in gerontoplasts of senescent leaves of vicia faba l.

1988 ◽  
Vol 43 (1-2) ◽  
pp. 149-154 ◽  
Author(s):  
H. Oskar Schmidt
Keyword(s):  
Vicia Faba ◽  
Thylakoid Membranes ◽  
Photochemical Activity ◽  
Structure And Function ◽  
Polypeptide Composition ◽  
Light Harvesting Complex ◽  
Vicia Faba L ◽  
Light Protection ◽  
Flotation Method ◽  
And Function

In the course of yellowing (senescence) the leaves of Vicia faba L. lose 95% of their chlorophyll. Gerontoplasts develop from chloroplasts and aggregate with the pycnotic mitochondria and the cell nucleus in the senescent cells (organelle aggregation). The gerontoplasts contain only a few, unstacked thylakoid membranes but a large number of carotinoid-containing plastoglobuli, which after the degration of chlorophyll presumably assume the light protection of the cells. The thylakoid membranes of the gerontoplasts were isolated by means of a flotation method. Their polypeptide composition is characterized by a high proportion of light-harvesting complex. Evidence of relatively high photochemical activity shows that functional thylakoid membranes are present in the premortal senescence state of leaves and this suggests that there is functional compartmentation of the hydrolytic processes in this stage of the leaves’ development

scholarly journals Probing the electric field across thylakoid membranes in cyanobacteria

2019 ◽  
Vol 116 (43) ◽  
pp. 21900-21906 ◽  
Author(s):  
Stefania Viola ◽  
Benjamin Bailleul ◽  
Jianfeng Yu ◽  
Peter Nixon ◽  
Julien Sellés ◽  
...  
Keyword(s):  
Electric Field ◽  
Photosynthetic Electron Transport ◽  
Thylakoid Membranes ◽  
Transport Pathways ◽  
Electrochromic Shift ◽  
Ideal Tool ◽  
Bona Fide ◽  
The Difference ◽  
And Function

In plants, algae, and some photosynthetic bacteria, the ElectroChromic Shift (ECS) of photosynthetic pigments, which senses the electric field across photosynthetic membranes, is widely used to quantify the activity of the photosynthetic chain. In cyanobacteria, ECS signals have never been used for physiological studies, although they can provide a unique tool to study the architecture and function of the respiratory and photosynthetic electron transfer chains, entangled in the thylakoid membranes. Here, we identified bona fide ECS signals, likely corresponding to carotenoid band shifts, in the model cyanobacteria Synechococcus elongatus PCC7942 and Synechocystis sp. PCC6803. These band shifts, most likely originating from pigments located in photosystem I, have highly similar spectra in the 2 species and can be best measured as the difference between the absorption changes at 500 to 505 nm and the ones at 480 to 485 nm. These signals respond linearly to the electric field and display the basic kinetic features of ECS as characterized in other organisms. We demonstrate that these probes are an ideal tool to study photosynthetic physiology in vivo, e.g., the fraction of PSI centers that are prebound by plastocyanin/cytochrome c6 in darkness (about 60% in both cyanobacteria, in our experiments), the conductivity of the thylakoid membrane (largely reflecting the activity of the ATP synthase), or the steady-state rates of the photosynthetic electron transport pathways.

The thylakoid membranes of cyanobacteria: structure, dynamics and function

1999 ◽  
Vol 26 (7) ◽  
pp. 671 ◽  
Author(s):  
Conrad W. Mullineaux
Keyword(s):  
Genetic Manipulation ◽  
Three Dimensional ◽  
Thylakoid Membranes ◽  
Model Systems ◽  
Photosynthetic Membrane ◽  
Membrane Function ◽  
Intact Membrane ◽  
Photosynthetic Organism ◽  
Dynamics And Function ◽  
And Function

In recent years there has been remarkable progress in determining the three-dimensional structures of photosynthetic complexes. A new challenge is emerging: can we understand the organisation and interaction of those complexes in the intact photosynthetic membrane? Intact membranes are complex, dynamic systems. If we are to understand the function of the intact membrane, we will need to understand the organisation of the complexes, how they can diffuse and interact in the membrane, how they are assembled, repaired and broken down, and how their function is regulated. Cyanobacteria have some crucial advantages as model systems. The complete sequencing of the Synechocystis 6803 genome, coupled with the ease of genetic manipulation of Synechocystis (and certain other cyanobacteria) have given us a unique tool for studying a photosynthetic organism. Furthermore, some cyanobacteria have a very simple, regular thylakoid membrane structure. The unique geometry of photosynthetic membranes of these cyanobacteria will greatly facilitate biophysical studies of membrane function. This review summarises recent progress in understanding the structure, function and dynamics of cyanobacterial thylakoid membranes, highlights the questions that remain to be answered and suggests some possible approaches towards solving those questions.

9-Aminoacridine Binding to Chloroplast Membranes in Dark. Reversal by Mg2+

1978 ◽  
Vol 33 (1-2) ◽  
pp. 108-112 ◽  
Author(s):  
Salil Bose ◽  
George E. Hodi
Keyword(s):  
Thylakoid Membranes ◽  
Fluorescence Yield ◽  
Structure And Function ◽  
Chloroplast Membranes ◽  
Chemical Binding ◽  
Apparent Binding Constant ◽  
Low Salt ◽  
Membrane Bound ◽  
And Function ◽  
Function Interpretation

Abstract 9-Aminoacridine (9AA) binds to photosynthetic m em branes of unilluminated chloroplasts in low-salt media. The binding was insensitive to the uncouplers of photophosphorylation. The apparent binding constant was 140 μM . The binding isotherm as a function of 9AA concentration was sigmoid, and approximately 3 mol 9AA/mol chlorophyll was bound at saturating concentrations of 9AA.Addition of Mg2+ partially reversed the binding of 9AA in chloroplasts in the dark as observed by a Mg2+-induced increase of 9AA fluorescence as well as by spectrophotom etric measurements of free 9AA. It appeared, however, that use of fluorescence techniques for m easuring free 9AA introduced an error in the estimation of the m agnitude of binding, particularly at low concentration of 9AA ( < 7 5 μM). This is probably due to change in fluorescence yield of membrane-bound 9AA on addition of cations. The nature of the binding of 9AA to the thylakoid membranes and the effects of Mg2+ thereupon suggest that both chemical binding of cations and screening of surface charge of the mem branes should be considered in discussing the mechanism of cation action on chloroplast structure and function. Interpretation of these data with respect to heterogeneity of sites of cation action upon or within chloroplast membranes is discussed.

Role of sulfolipds in grana thylakoid stacking

1990 ◽  
Vol 48 (3) ◽  
pp. 666-667
Author(s):  
Lorenzo W. Coats
Keyword(s):  
Higher Plants ◽  
Thylakoid Membranes ◽  
Nacl Solution ◽  
Membrane Structure And Function ◽  
Low Salt ◽  
Stroma Lamellae ◽  
Thylakoid Stacking ◽  
The Subject ◽  
And Function

In higher plants and algae, the thylakoid membranes are organized into closely appressed or stacked regions (grana), and a network of single interconnecting unstacked regions (stroma lamellae). The components and forces responsible for adhesion between thylakoids have been the subject of intense studies. Although these studies have added significantly to our knowledge of chloroplast membrane structure and function, they have failed to provide a clear rationale for grana membrane stacking. Completedestacking of grana occurs when chloroplasts are suspended in low-salt (10 mM NaCl) solution. Normal levels of stacked and un-stacked regions can be restored by incubation in salt solutions (150 mM NaCl).

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