Fingerprinting the macro-organisation of pigment–protein complexes in plant thylakoid membranes in vivo by circular-dichroism spectroscopy

• Published in: Biochimica et biophysica acta 2016-09, Vol.1857 (9), p.1479-1489
• Main Authors: Tóth, Tünde N., Rai, Neha, Solymosi, Katalin, Zsiros, Ottó, Schröder, Wolfgang P., Garab, Győző, van Amerongen, Herbert, Horton, Peter, Kovács, László
• Format: Article
• Language: English
• Subjects: 1976; 2011; BIOCHEMICAL JOURNAL; Chiral macrodomain; Chloroplasts - ultrastructure; Circular Dichroism; i-type CD; Light-harvesting complexes; Light-Harvesting Protein Complexes - chemistry; METER S; P2659; P469 Bianchi Silvia; Photosystem II Protein Complex - chemistry; Photosystem II supercomplexes; PLANT CELL; Plant Leaves - chemistry; Psi-type CD; Thylakoid membrane; Thylakoids - chemistry; V156; V23; Xanthophylls - chemistry
• ISSN: 0005-2728; 0006-3002; 1879-2650; 1879-2650
• DOI: 10.1016/j.bbabio.2016.04.287

Macro-organisation of the protein complexes in plant thylakoid membranes plays important roles in the regulation and fine-tuning of photosynthetic activity. These delicate structures might, however, undergo substantial changes during isolating the thylakoid membranes or during sample preparations, e.g., for electron microscopy. Circular-dichroism (CD) spectroscopy is a non-invasive technique which can thus be used on intact samples. Via excitonic and psi-type CD bands, respectively, it carries information on short-range excitonic pigment–pigment interactions and the macro-organisation (chiral macrodomains) of pigment–protein complexes (psi, polymer or salt-induced). In order to obtain more specific information on the origin of the major psi-type CD bands, at around (+)506, (−)674 and (+)690nm, we fingerprinted detached leaves and isolated thylakoid membranes of wild-type and mutant plants and also tested the effects of different environmental conditions in vivo. We show that (i) the chiral macrodomains disassemble upon mild detergent treatments, but not after crosslinking the protein complexes; (ii) in different wild-type leaves of dicotyledonous and monocotyledonous angiosperms the CD features are quite robust, displaying very similar excitonic and psi-type bands, suggesting similar protein composition and (macro-) organisation of photosystem II (PSII) supercomplexes in the grana; (iii) the main positive psi-type bands depend on light-harvesting protein II contents of the membranes; (iv) the (+)506nm band appears only in the presence of PSII–LHCII supercomplexes and does not depend on the xanthophyll composition of the membranes. Hence, CD spectroscopy can be used to detect different macro-domains in the thylakoid membranes with different outer antenna compositions in vivo. •CD spectroscopy was used for fingerprinting the PSII macrodomains in vivo.•The PSII–LHCII supercomplex is a prerequisite for the native CD fingerprint.•LHCII composition determines the CD spectra via influencing the PSII macro-structures.