PARENT SESSION

Symposium S8B Supermolecular organization of the photosynthetic apparatus
Friday September 3rd, 2004 8:30 AM-10:30 AM Room 210A
Chair: Jan Dekker
Co-Chair: André Verméglio

Crystal structure of plant Photosystem I - A super complex of reaction center and LHC. Nathan Nelson^*,1, Felix Frilow¹, Adam Ben-Shem¹, ¹ Faculty of Life Sciences, Tel Aviv, 69978, Israel

ABSTRACT- Crystal Structure of Plant Photosystem I - a super complex of reaction center and LHC Adam Ben-Shem , Felix Frolow and Nathan Nelson The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel Oxygenic photosynthesis is driven by two multi-subunit membrane proteins complexes, photosystem I and photosystem II. We determined the crystal structure of the complete photosystem I (PSI) from a higher plant to 4.4 A resolution. The structure shows 12 core subunits, 4 different light-harvesting proteins (LHCI) assembled in a half moon shape on one side of the core, 45 transmembrane helices, 167 chlorophylls, 3 Fe-S clusters and 2 phylloquinones. The peripheral antenna of PSI is composed of four gene products (Lhca1-4) that are unique among the chlorophyll a/b binding proteins in their pronounced long-wavelength absorbance and in their assembly into dimers. The structure of plant photosystem I provides the first relatively high-resolution structural model of a super-complex containing a reaction center and its peripheral antenna. The structural features responsible for the unique properties of LHCI will be discussed. Possible modes of interaction with LHCII, plastocyanin and ferredoxin will be proposed.

KEY WORDS: Stucture, Photosystem I, LHCI, Crystal