Towards a structure of green plant Photosystem II

Michal Kutý^1,4, Jaroslava Kohoutová¹, Jiří Heler^1,2, Marie Plevako^1,2, Tatsiana Holubeva¹, Daryna Kulik¹, Ondrej Šedo³, Zbyněk Zdrahal³, Ivana Kutá Smatanová ^1,4

¹ University of South Bohemia in České Budějovice, School of komplex systems FFPW , Zámek 136, 373 33 Nové Hrady

² University of South Bohemia in České Budějovice, Faculty of Science, Branišovská 31, 37005 České Budějovice

³Core Facility – Proteomics, CEITEC, Masaryk University, Kamenice 5,625 00 Brno

⁴ Academy of Sciences of the Czech Republic, Inst. of Nanobiology and Structural Biology GCRC, Zámek 136, 373 33 Nové Hrady

Photosystem II (PSII) is a pigment-protein complex of thylakoid membrane in cyanobacteria, algae and higher plants. PSII performs series of light driven reactions resulting in charge separation and subsequently in a reduction of an electron-transport chain and water oxidation. Primary site of the light to chemical energy conversion is located in so-called reaction center (RC).

PSII is a multisubunit complex embedded in the thylakoid membrane of plants, algae and cyanobacteria The function of the PSII in different organisms is identical while the composition of their subunits is different. Recently the 3D X-ray structures of cyanobacterial PSII were determined to the maximum resolution of 2.9Ǻ. Cyanobacterial PSII consists of different extrinsic proteins compared with plant PSII and also the light-harvesting complex is not bound in thylakoid membrane to PSII core as it is in plant PSII.

Nowadays we are developing model of thylakoid photosynthetical membrane (glycolipid membrane instead of our previous octane layer) to build complex model of PSII RC.

In a paralell direction to theoretical approach we are focused on hydroponic plant growth hunder controlled conditions and optimization of reproducible purification protocol of homogeneous sample suitable for crystallization. Few types of higher plants like model organisms were chosen (tobacco, spinach, pea, haricot and soya). It was shown that the type of detergent and conditions of solubilization of thylakoid membranes are critical steps, which should be carefully chosen.