Small-angle neutron scattering study of the ultrastructure of chloroplast thylakoid membranes - periodicity and structural flexibility of the stroma lamellae
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Dorthe Posselt, Gergely Nagy, Jacob Judas Kain Kirkensgaard, Jens K. Holm, Thomas H. Aagaard, Peter Timmins, Eszter Rétfalvi, László Rosta, László Kovács, Gyözö Garab
Source: Biochimica et Biophysica Acta (BBA) - Bioenergetics, Available online 28 January 2012
Dorthe Posselt, Gergely Nagy, Jacob J.K. Kirkensgaard, Jens K. Holm, Thomas H. Aagaard, ...
The multilamellar organisation of freshly isolated spinach and pea chloroplast thylakoid membranes was studied using small-angle neutron scattering. A broad peak at ~ 0.02 Åis ascribed to diffraction from domains of ordered, unappressed stroma lamellae, revealing a repeat distance of 294 Å ± 7 Å in spinach and 345 Å ± 11 Å in pea. The peak position and hence the repeat distance of stroma lamellae is strongly dependent on the osmolarity and the ionic strength of the suspension medium, as demonstrated by varying the sorbitol and the Mg-concentration in the sample. For pea thylakoid membranes, we show that the repeat distance decreases when illuminating the sample with white light, in accordance with our earlier results on spinach, also regarding the observation that addition of an uncoupler prohibits the light-induced structural changes, a strong indication that these changes are driven by the transmembrane proton gradient. We show that the magnitude of the shrinkage is strongly dependent on light intensity and that the repeat distance characteristic of the dark state after illumination is different from the initial dark state. Prolonged strong illumination leads to irreversible changes and swelling as reflected in increased repeat distances. The observed reorganizations are discussed within the frames of the current structural models of the granum stroma thylakoid membrane assembly and the regulatory mechanisms in response to variations in the environmental conditionsin vivo. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Articifical Photosynthesis.
Highlights¿ Small-angle neutron scattering peak arising from stroma lamellae is identified ¿ Stroma lamellar repeat distances at different ionic strengths and osmotic pressures ¿ Light-induced reversible reorganizations of thylakoid membranes monitored by SANS ¿ Preillumination-dependent dark-state periodicity of the stroma lamellae
|Journal||Biochimica et Biophysica Acta (BBA) - Bioenergetics|
|Publication status||Published - 1 Jan 2012|