During the donor-side photoinhibition of spinach photosystem II, the reaction center D1 protein cross-linked with the antenna chlorophyll binding protein CP43 of photosystem II lacking the oxygen-evolving complex (OEC) subunit proteins. The cross-linking did not occur upon illumination of photosystem II samples that retained the OEC33, nor when OEC33-depleted photosystem II samples were reconstituted with the OEC33 prior to illumination. These results suggest that the D1 protein, CP43 and the OEC33 are located in close proximity at the lumenal side of photosystem II, and that the OEC33 suppresses the unnecessary contact between the D1 protein and CP43. Previously we presented data showing the D1 protein located adjacent to CP43 on the stromal side of photosystem II [Ishikawa et al. (1999) Biochim. Biophys. Acta 1413: 147]. The present data suggest that the spatial arrangement of the D1 protein and CP43 at the lumenal side of photosystem II in spinach chloroplasts is similar to that at the stromal side of photosystem II and is consistent with the assignment of these proteins recently proposed on the crystal structures of the photosystem II complexes from cyanobacteria [Zouni et al. (2001) Nature 409: 739, Kamiya and Shen 2003 Proc. Natl. Acad. Sci. USA, 100: 98]. Moreover, the data suggest that the binding condition and positioning of the OEC33 in the photosystem II complex from higher plants may be different from those in cyanobacteria.
Keywords: Keywords: CP43 — D1 protein — OEC33 — Photosystem II — Protein cross-linking.; Abbreviations: PSI and PSII, photosystem I and II; D1 and D2, the reaction center-binding proteins of PSII; CP43 and CP47, the antenna chlorophyll-binding proteins of PSII; P680, the primary electron donor in PSII; Try Z, tyrosine secondary electron donor in PSII; OEC33, 24 and 18, the extrinsic 33, 24 and 18 kDa protein subunit constituting the oxygen-evolving complex of PSII; Cyt, cytochrome.
Journal Article. 3732 words. Illustrated.
Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry
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