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Title: IDENTIFICATION OF NOVEL POLYPEPTIDES IN A HIGHLY PURIFIED PHOTOSYSTEM II PREPARATION FROM THE CYANOBACTERIUM SYNECHOCYSTIS SP.PCC 6803

Author
item KASHINO, Y - HIMEJI INSTITUTE JAPAN
item LUABER, W - PHARMUCIN ST LOUIS MO
item CARROLL, J - PHARMUCIN ST LOUIS MO
item WANG, Q - UNIV OF ILLINOIS URBANA
item WHITMARSH, CLIFFORD
item SATOH, K - HIMEJI INSTITUTE JAPAN
item PAKRASI, H - WASHINGTON STATE UNIV MO

Submitted to: Journal of Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/25/2001
Publication Date: 12/20/2001
Citation: 12th International Congress on Photosynthesis. CSIRO Publishing: Melbourne, Austrialia. 2001.

Interpretive Summary: In plants the light driven electron transport reactions of photosynthesis depend on two protein complexes, photosystem II and photosystem I, that are located in the photosynthetic membrane of chloroplasts. These two specialized proteins are surrounded by an antenna system that gathers light and transfers the energy to the photosystems. Photosystem II uses the light energy to extract electrons from water molecules and sends the electrons via an electron transport pathway to photosystem I. The removal of electrons from water is the source of the molecular oxygen in the earth's atmosphere. Based on decades of research we now have a clear picture of how the light driven chemistry operates. However, due to the fact that photosystem II creates some of the strongest oxidants and reductants found in biology, the complex is subject to damage. As a consequence plants have developed protective and repair mechanisms that are only now becoming evident. The goal of this project is to isolate active photosystem II complexes from photosynthetic membranes that provide a robust system for determining the structure of photosystem II and studying how photosystem II operates and protects itself from photodamage. This preparation will be useful to research scientists investigating the molecular basis of photosynthetic performance and stability.

Technical Abstract: Highly active oxygen-evolving photosystem II complexes were purified from a mutant of Synechocystis 6803 His-tugged. Measurements of oxygen evolution, chlorophyll fluorescence indicate that donor and acceptor sides of purified complexes are intact and active. A detailed analysis of polypeptide composition using a system designed to enhance resolution of low molecular weight polypeptides, followed by N-terminal amino acid sequencing and matrix assisted laser desorption (MALDI) mass spectrometry, identified over 24 polypeptides in purified PSII complex. Nineteen of the polypeptides have previously been shown to be part of other purified photosystem II preparations. Among the novel polypeptides are PsbJ and PsbY, which have shown to be necessary for synthesis of active PSII complexes by gene deletion, but until now have not been shown to be part of active PSII complexes. Additional polypeptides that have not been previously detected in PSII preparations from cyanobacteria include: the sll1638 gene product, which is highly homologous to peripheral 17 kDa protein (PsbQ) found in plant PS II complexes; FtsH, which was identified as a protease of D1 protein, and ycf9 gene product (Orf62 in plants), which had previously been identified in chloroplast stromal membranes. This work describes photosystem II preparation containing newly identified polypeptides that can be used to investigate the structure, function, biogenesis of photosystem II.