Light-harvesting complex II (LHCII) and its supramolecular organization in Chlamydomonas reinhardtii

• Published in: Biochimica et biophysica acta Vol. 1837; no. 1; pp. 63 - 72
• Main Authors: Drop, Bartlomiej, Webber-Birungi, Mariam, Yadav, Sathish K.N., Filipowicz-Szymanska, Alicja, Fusetti, Fabrizia, Boekema, Egbert J., Croce, Roberta
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.01.2014
• Subjects: Chlamydomonas reinhardtii; Chlamydomonas reinhardtii - chemistry; Chlorophyll - chemistry; Dimerization; Electron microscopy; Energy Transfer; Light; Light harvesting complexes organization; Light-Harvesting Protein Complexes - chemistry; Molecular Conformation; Phosphorylation; Photosynthesis; Photosystem II; Photosystem II Protein Complex - chemistry; Plants - chemistry; Thylakoids - metabolism; Light harvesting complexes organization; Photosystem II; Photosynthesis; Electron microscopy; Chlamydomonas reinhardtii
• ISSN: 0005-2728; 0006-3002; 1879-2650
• DOI: 10.1016/j.bbabio.2013.07.012

LHCII is the most abundant membrane protein on earth. It participates in the first steps of photosynthesis by harvesting sunlight and transferring excitation energy to the core complex. Here we have analyzed the LHCII complex of the green alga Chlamydomonas reinhardtii and its association with the core of Photosystem II (PSII) to form multiprotein complexes. Several PSII supercomplexes with different antenna sizes have been purified, the largest of which contains three LHCII trimers (named S, M and N) per monomeric core. A projection map at a 13Å resolution was obtained allowing the reconstruction of the 3D structure of the supercomplex. The position and orientation of the S trimer are the same as in plants; trimer M is rotated by 45° and the additional trimer (named here as LHCII-N), which is taking the position occupied in plants by CP24, is directly associated with the core. The analysis of supercomplexes with different antenna sizes suggests that LhcbM1, LhcbM2/7 and LhcbM3 are the major components of the trimers in the PSII supercomplex, while LhcbM5 is part of the “extra” LHCII pool not directly associated with the supercomplex. It is also shown that Chlamydomonas LHCII has a slightly lower Chlorophyll a/b ratio than the complex from plants and a blue shifted absorption spectrum. Finally the data indicate that there are at least six LHCII trimers per dimeric core in the thylakoid membranes, meaning that the antenna size of PSII of C. reinhardtii is larger than that of plants. •The structure of PSII–LHCII complex of C. reinhardtii was obtained at a 13Å resolution.•3 LHCII trimers are associated with the core and 3 additional ones are present in the membrane.•Position and orientation of the three trimers in the supercomplex (S, M and N) were determined.•LhcbM1, 2/7 and 3 are the main LHCII components.•C. reinhardtii LHCII absorption spectrum is blue shifted compared to that of plant LHCII.