title: Coupled rows of PBS cores and PSII dimers in cyanobacteria: symmetry and structure.
abstract: Phycobilisome (PBS) is a giant water-soluble photosynthetic antenna transferring the energy of absorbed light mainly to the photosystem II (PSII) in cyanobacteria. Under the low light conditions, PBSs and PSII dimers form coupled rows where each PBS is attached to the cytoplasmic surface of PSII dimer, and PBSs come into contact with their face surfaces (state 1). The model structure of the PBS core that we have developed earlier by comparison and combination of different fine allophycocyanin crystals, as reported in Zlenko et al. (Photosynth Res 130(1):347-356, 2016b), provides a natural way of the PBS core face-to-face stacking. According to our model, the structure of the protein-protein contact between the neighboring PBS cores in the rows is the same as the contact between the APC hexamers inside the PBS core. As a result, the rates of energy transfer between the cores can occur, and the row of PBS cores acts as an integral PBS "supercore" providing energy transfer between the individual PBS cores. The PBS cores row pitch in our elaborated model (12.4 nm) is very close to the PSII dimers row pitch obtained by the electron microscopy (12.2 nm) that allowed to unite a model of the PBS cores row with a model of the PSII dimers row. Analyzing the resulting model, we have determined the most probable locations of ApcD and ApcE terminal emitter subunits inside the bottom PBS core cylinders and also revealed the chlorophyll molecules of PSII gathering energy from the PBS.
authors.affiliation: Biological Faculty of M.V. Lomonosov Moscow State University, Lenin Hills, 1/12, Moscow, Russia, 119991. dvzlenko@gmail.com.|K.A. Timiryazev Institute of Plant Physiology RAS, Botanicheskaya St, 35, Moscow, Russia, 127276. dvzlenko@gmail.com.
authors.forename: Dmitry V
authors.initials: DV
authors.lastname: Zlenko
authors.affiliation: Biological Faculty of M.V. Lomonosov Moscow State University, Lenin Hills, 1/12, Moscow, Russia, 119991.|INRIA Team Dracula, INRIA Antenne Lyon la Doua, 69603, Villeurbanne, France.|Institut Camille Jordan, UMR 5208 CNRS, University Lyon 1, 69622, Villeurbanne, France.
authors.forename: Tatiana V
authors.initials: TV
authors.lastname: Galochkina
authors.affiliation: Biological Faculty of M.V. Lomonosov Moscow State University, Lenin Hills, 1/12, Moscow, Russia, 119991.|K.A. Timiryazev Institute of Plant Physiology RAS, Botanicheskaya St, 35, Moscow, Russia, 127276.
authors.forename: Pavel M
authors.initials: PM
authors.lastname: Krasilnikov
authors.affiliation: K.A. Timiryazev Institute of Plant Physiology RAS, Botanicheskaya St, 35, Moscow, Russia, 127276.
authors.forename: Igor N
authors.initials: IN
authors.lastname: Stadnichuk
mesh_terms: D018360:Crystallography, X-Ray; D000458:Cyanobacteria / Q000378:metabolism*; D008958:Models, Molecular; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000378:metabolism*; D045524:Phycobilisomes / Q000378:metabolism*; D055503:Protein Multimerization; D053545:Spirulina / Q000378:metabolism
chemical_list: D045332:Photosystem II Protein Complex; D045524:Phycobilisomes
keywords: Coupled rows; Photosystem II; Phycobilisome; State transitions; Terminal emitters