Crystals of photosystem II core complex from Pisum sativum

Ivana Kutá Smatanová^{1, 2}, José A. Gavira³ , Pavlína Řezáčová⁴, František Vácha^{1, 5}, and Juan M. Garcia-Ruiz³

¹Institute of Physical Biology USB CB, Zámek 136, 373 33 Nové Hrady, Czech Republic
²Institute of Systems Biology and Ecology AS CR Zámek 136, 373 33 Nové Hrady, Czech Republic
³Laboratorio de Estudios Cristalografico, Edificio BIC-Granada, Avda. de la Innovacion 1, P.T. Ciencias de la Salud, 18100-Armilla, Granada, Spain
⁴Dep. Biochemistry, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas,
Texas 75390-8816

⁵Institute of Plant Molecular Biology AS CR, Branišovská 31, 370 05 České Budějovice,
Czech Republic

The photosystem II (PSII), the system where oxygenic photosynthesis in plants, algae and cyanobacteria is initiated, is a homodimeric multisubunit protein-cofactor complex consisting of membrane in-lying subunits, hydrophilic peripheral subunits and large number of cofactors as chlorophylls, pheophytins, carothenoids, plastoquinones, iron and manganese, which together trap, transfer and modulate a sunlight and drive the unique photoinduced oxidation of water to atmospheric oxygen. Catalytic mechanism of PSII has been studied using a wide range of approaches [1-3], but particular molecular details of water oxidation catalyzed by the oxygen evolving center (OEC) remains unclear. Crystallographic studies of cyanobacterial OEC PSII from thermophilic cyanobacterium have provided several medium-resolution structures from resolution 3.8Å to 3.2Å [4-6]. Results of mentioned studies have given the first description of the structure of PSII, but present models are not absolutely complete as yet.

Finding suitable crystallization condition is the main problem to solve a protein structure by X-ray diffraction techniques. The current crystallization strategies are mainly based on the screening upon previously successful chemical cocktails and on classical crystallization techniques based on evaporation. That strategy has been found partially successful for soluble globular proteins. However, membrane protein is a particular case for which the success rate applying commercial crystallization screens is much lower than for soluble proteins. The fact that membrane proteins are often unstable, highly temperature and light sensitive together with their complicated composition are responsible for difficult crystal growing and solving their structure.

Crystallization experiments of monomeric and dimeric photosystem II core complex (OEC PSII) from Pisum sativum have been already described [7]. Here we report following experiments aimed at obtaining better-quality crystals suitable for diffraction analysis. We have studied the influence of additives (MgCl₂, MgSO₄, MnCl₂, MnSO₄, (NH₄)₂SO₄, CdSO₄) and detergents (DM, LDAO, CAPS and Zwittergent 3-12) on the crystallization behavior of protein complex. We expect to obtain typical photosystem II core complex crystals for initial crystallographic characterization.

This work is supported by the Grant Agency of the Czech Republic (grant 206/03/D061), by the joint C.S.I.C. and AS CR project 2004CZ0003 in the frame of the cooperation agreement P2004CZ01, by the Ministry of Education of the Czech Republic (MSM6007665808) and by the Academy of Sciences of the Czech
Republic (Institutional research concept AVOZ60870520).

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