Role of Protein-Water Interface in the Stacking Interactions of Granum Thylakoid Membranes—As Revealed by the Effects of Hofmeister Salts

Abstract

The thylakoid membranes of vascular plants are differentiated into stacked granum and unstacked stroma regions. The formation of grana is triggered by the macrodomain formation of photosystem II and light-harvesting complex II (PSII-LHCII) and thus their lateral segregation from the photosystem I-light-harvesting complex I (PSI-LHCI) supercomplexes and the ATP-synthase; which is then stabilized by stacking interactions of the adjacent PSII-LHCII enriched regions of the thylakoid membranes. The self-assembly and dynamics of this highly organized membrane system and the nature of forces acting between the PSII-LHCII macrodomains are not well understood. By using circular dichroism (CD) spectroscopy, small-angle neutron scattering (SANS) and transmission electron microscopy (TEM), we investigated the effects of Hofmeister salts on the organization of pigment-protein complexes and on the ultrastructure of thylakoid membranes. We found that the kosmotropic agent (NH 4) 2 SO 4 and the Hofmeisterneutral NaCl, up to 2 M concentrations, hardly affected the macro-organization of the protein complexes and the membrane ultrastructure. In contrast, chaotropic salts, NaClO 4 , and NaSCN destroyed the mesoscopic structures, the multilamellar organization of the thylakoid membranes and the chiral macrodomains of the protein complexes but without noticeably affecting the short-range, pigment-pigment excitonic interactions. Comparison of the concentration-and time-dependences of SANS, TEM and CD parameters revealed the main steps of the disassembly of grana in the presence of chaotropes. It begins with a rapid diminishment of the long-range periodic order of the grana membranes, apparently due to an increased stacking disorder of the thylakoid membranes, as reflected by SANS experiments. SANS measurements also allowed discrimination between the cationic and anionic effects-in stacking and disorder, respectively. This step is followed by a somewhat slower disorganization of the TEM

Accumulation of geranylgeranylated chlorophylls in the pigment-protein complexes of Arabidopsis thaliana acclimated to green light: effects on the organization of light-harvesting complex II and photosystem II functions

“…Moreover, the (−) 673 nm band is preferentially associated with grana stacking (Garab et al 1991 ), whereas the (+) 505 and (+) 685 nm bands do not depend directly on the granal stacking, but rather on the lateral supramolecular organization of PSII and PSII–LHCII supercomplexes (Tóth et al 2016 ; Kovács et al 2006 ). Therefore, these results suggest that acclimation to GL leads to a reduced chiral macro-organization of LHCII–PSII supercomplexes, while not affecting the formation of LHCII trimers and granal stacking, which result from subtle interplays of physicochemical forces of repulsion and attraction within chloroplasts with LHCII trimers playing significant roles (Anderson et al 2008 ; Chow et al 2005 ; Zsiros et al 2020 ). This is in line with the electrophoretic data that revealed lower content of LHCII–PSII supercomplexes and, on the contrary, higher content of LHCII unbound to PSII in GL acclimated plants compared to control plants (Fig.…”

Excitation energy transfer kinetics of trimeric, monomeric and subunit-depleted Photosystem I from Synechocystis PCC 6803

“…Molar absorption coefficients were taken from Lichtenthaler [44]. For analysis of the Chls and Cars composition by high-performance liquid chromatography, the pigments were extracted in pure acetone and the quantification was performed using a Shimadzu Prominence HPLC system as described in Zsiros et al [45]. The pigments were identified according to their retention time and absorption spectrum and quantified by integrated chromatographic peak area recorded at the wavelength of maximum absorbance for each kind of pigments using the corresponding molar decadic absorption coefficient [46].…”

Fine Mapping and Identification of BnaC06.FtsH1, a Lethal Gene That Regulates the PSII Repair Cycle in Brassica napus

“…FtsH1 participates in the formation of the hetero-hexameric complex and regulation of thylakoid membrane biogenesis [ 25 ]. Meanwhile, thylakoid membranes are densely packed with pigment–protein complexes of PSII and PSI [ 26 ], lack of chlorophyll and carotenoids in the mutant may cause PSII and chloroplast abnormalities. Therefore, plump chloroplast structures and stacked thylakoid membranes were not observed in mutant 7-521Y.…”