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J Biol Chem. 2014 Jul 18;289(29):20150-7. doi: 10.1074/jbc.M114.574822. Epub 2014 Jun 9.

Cross-linking evidence for multiple interactions of the PsbP and PsbQ proteins in a higher plant photosystem II supercomplex.

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From the Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan.
the School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, United Kingdom, and.
the Plant Global Educational Project, Nara Institute of Science and Technology, Ikoma 630-0192, Japan.
From the Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan,


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.


Extrinsic Protein; Mass Spectrometry (MS); Oxygen-evolving Complex; Photosystem II; Plant Biochemistry; Protein Cross-linking; Western Blot

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