title: Cross-linking evidence for multiple interactions of the PsbP and PsbQ proteins in a higher plant photosystem II supercomplex.
abstract: The extrinsic subunits of membrane-bound photosystem II (PSII) maintain an essential role in optimizing the water-splitting reaction of the oxygen-evolving complex (OEC), even though they have undergone drastic change during the evolution of oxyphototrophs from symbiotic cyanobacteria to chloroplasts. Two specific extrinsic proteins, PsbP and PsbQ, bind to the lumenal surface of PSII in green plants and maintain OEC conformation and stabilize overall enzymatic function; however, their precise location has not been fully resolved. In this study, PSII-enriched membranes, isolated from spinach, were subjected to chemical cross-linking combined with release-reconstitution experiments. We observed direct interactions between PsbP and PsbE, as well as with PsbR. Intriguingly, PsbP and PsbQ were further linked to the CP26 and CP43 light-harvesting proteins. In addition, two cross-linked sites, between PsbP and PsbR, and that of PsbP and CP26, were identified by tandem mass spectrometry. These data were used to estimate the binding topology and location of PsbP, and the putative positioning of PsbQ and PsbR on the lumenal surface of the PSII. Our model gives new insights into the organization of PSII extrinsic subunits in higher plants and their function in stabilizing the OEC of the PSII supercomplex.
authors.affiliation: From the Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Kunio
authors.initials: K
authors.lastname: Ido
authors.affiliation: the School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, United Kingdom, and.
authors.forename: Jon
authors.initials: J
authors.lastname: Nield
authors.affiliation: the Plant Global Educational Project, Nara Institute of Science and Technology, Ikoma 630-0192, Japan.
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Fukao
authors.affiliation: From the Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Taishi
authors.initials: T
authors.lastname: Nishimura
authors.affiliation: From the Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Sato
authors.affiliation: From the Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan, ifuku@kais.kyoto-u.ac.jp.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Ifuku
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D003432:Cross-Linking Reagents; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D054730:Protein Interaction Domains and Motifs; D020836:Protein Structure, Quaternary; D021122:Protein Subunits; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018724:Spinacia oleracea / Q000235:genetics / Q000378:metabolism; D053719:Tandem Mass Spectrometry
chemical_list: D003432:Cross-Linking Reagents; D045332:Photosystem II Protein Complex; D021122:Protein Subunits; D011994:Recombinant Proteins
keywords: Extrinsic Protein; Mass Spectrometry (MS); Oxygen-evolving Complex; Photosystem II; Plant Biochemistry; Protein Cross-linking; Western Blot