Takasaka, Kenji Division of Bioscience, Graduate School of Natural Science and Technology/Faculty of Science; Okayama University
Iwai, Masako Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science
Umena, Yasufumi Department of Chemistry, Graduate School of Science, Osaka City University
Kawakami, Keisuke Division of Bioscience, Graduate School of Natural Science and Technology/Faculty of Science; Okayama University
Ohmori, Yukari Division of Bioscience, Graduate School of Natural Science and Technology/Faculty of Science; Okayama University
Ikeuchi, Masahiko Department of Life Sciences (Biology), Graduate School of Arts and Science, The University of Tokyo
Takahashi, Yuichiro Division of Bioscience, Graduate School of Natural Science and Technology/Faculty of Science; Okayama University Kaken ID researchmap
Kamiya, Nobuo Department of Chemistry, Graduate School of Science, Osaka City University
Ycf12 (Psb30) and PsbZ are two low molecular weight subunits of photosystem II (PSII), with one and two trans-membrane helices, respectively. In order to study the functions of these two subunits from a structural point of view, we constructed deletion mutants lacking either Ycf12 or PsbZ from Thermosynechococcus elongatus, and purified, crystallized and analyzed the structure of PSII dimer from the two mutants. Our results showed that Ycf12 is located in the periphery of PSII, close to PsbK, PsbZ and PsbJ, and corresponded to the unassigned helix X1 reported previously, in agreement with the recent structure at 2.9 Å resolution (A. Guskov, J. Kern, A. Gabdulkhakov, M. Broser, A. Zouni, W. Saenger, Cyanobacterial photosystem II at 2.9 Å resolution: role of quinones, lipids, channels and chloride, Nat. Struct. Mol. Biol. 16 (2009) 334–342). On the other hand, crystals of PsbZ-deleted PSII showed a remarkably different unit cell constants from those of wild-type PSII, indicating a role of PsbZ in the interactions between PSII dimers within the crystal. This is the first example for a different arrangement of PSII dimers within the cyanobacterial PSII crystals. PSII dimers had a lower oxygen-evolving activity from both mutants than that from the wild type. In consistent with this, the relative content of PSII in the thylakoid membranes was lower in the two mutants than that in the wild type. These results suggested that deletion of both subunits affected the PSII activity, thereby destabilized PSII, leading to a decrease in the PSII content in vivo. While PsbZ was present in PSII purified from the Ycf12-deletion mutant, Ycf12 was present in crude PSII but absent in the finally purified PSII from the PsbZ-deletion mutant, indicating a preferential, stabilizing role of PsbZ for the binding of Ycf12 to PSII. These results were discussed in terms of the PSII crystal structure currently available
Biochimica et Biophysica Acta (BBA) - Bioenergetics
Elsevier Science BV.
© 2009 Elsevier B.V. All rights reserved.
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