PARENT SESSION
Posters P7B Evolution of photosynthesis. Abstracts (579-591)

Distribution of green sulfur bacteria type FNR in various bacteria and archaea. Daisuke Seo^*,1, Kei Kamino², Kazuhito Inoue³, Hidehiro Sakurai^{3, 4}, ¹ Department of Chemistry, Faculty of Science, Kanazawa University, Kanazawa, Ishikawa, Japan² Marine Biotechnology Institute, Kamaishi, Iwate, Japan³ Department of Bioscience, Faculty of Science, Kanagawa University, Hiratsuka, Kanagawa, Japan⁴ Department of Biology, School of Education, Waseda University, Shinjuku, Tokyo, Japan

ABSTRACT- We purified novel type ferredoxin-NADP⁺ reductase (FNR) from Chlorobium tepidum and Bacillus subtilis. The deduced molecular masses of these FNRs estimated by SDS-PAGE are about 40 kDa, well corresponding to the deduced mass from its genes, and those of the native form were estimated about 90 kDa by gel-permeation chromatography, indicating these FNRs exist as homodimer under physiological conditions. These FNRs contain one FAD per subunit and efficiently catalyze electron transfer reaction between NAD(P)H and Fd purified from each bacteria. From N-terminal amino acid sequence, the genes encoding these FNR polypeptides are identified to be CT1512 of C. tepidum, and yumC of B. subtilis. These genes encode the proteins with high similarity to NADPH-thioredoxin reductases (TR) and relatively low similarity to FNRs from gamma proteobacteria and various eukaryotes including oxygen-evolving photosynthetic organisms. However, a disulfide reduction motif conserved in authentic TR is missing in these genes. Homology search revealed this type of genes present in most of gram-positive bacteria except for clostridia, and less frequently in archaea and proteobacteria representing this type of FNRs constitute a new group of FNR which should be added to the already established plant type, bacteria type, and mitochondria type FNR groups.

KEY WORDS: NADPH thioredoxin reductase, ferredoxin NADPH oxidoreductase, green sulfur bacteria, Bacillus subtilis