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Updated: Sep 21, 2026

On-Chip Crystallization and Large-Scale Serial Diffraction at Room Temperature
Published on: March 11, 2022
Crystallization and preliminary crystallographic studies on the extrinsic 23 kDa protein in the oxygen-evolving
Kentaro Ifuku1, Toru Nakatsu, Hiroaki Kato
1Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kitashirakawa, Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan.
Abstract:
The extrinsic 23 kDa protein in the oxygen-evolving complex (OEC23 or PsbP) of photosystem II (PS II) helps to retain calcium and chloride ions, which are essential cofactors for the photosynthetic evolution of oxygen. OEC23 is found in the PS II complex from higher plants and green algae, but not in that from cyanobacteria or other ancestral photosynthetic organisms. In order to elucidate the three-dimensional structure and its molecular evolution, OEC23 was crystallized by the hanging-drop vapour-diffusion technique with PEG 4000 as a precipitant. Diffraction data to a resolution of 2.0 A were collected from a native crystal belonging to space group P2(1)2(1)2, with unit-cell parameters a = 91.36, b = 74.15, c = 52.16 A.
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