Poster: Enzymology

Abs # 251: Characterization of FNR from eukaryotic primitive red alga, Cyanidium caldarium

Presenter:	Wada, Keishiro , keiwada@kenroku.kanazawa-u.ac.jp
Authors	Wada, Keishiro  (A)   Fujiwara, Tatsuki  (A)   Enami, Isao  (B)   Sakamoto, Toshio  (A)
Affiliations:	(A): Division of Life Science, Graduate School of Natural Science and Technology, Kanazawa University (B): Department of Biology, Faculty of Science, Tokyo University of Science

In higher plants, matured FNR (ferredoxin-NADP⁺ oxidoreductase) encoded in petH gene is composed of two domains, FAD and NADP⁺ binding domains. It has proposed by Schluchter and Bryant (1992) that cyanobacterial FNRs have another CpcD-like domain in an N-terminal region, in addition to these two domains, and locate on the surface of phycobilisomes. Nakajima et al. (2002) reported the purification and characterization of FNR bound to phycobiliprotein from thermophilic cyanobacterium, Synechococcus elongatus and proved the proposal by Schluchter and Bryant. It is a very interesting matter that CpcD-like domain is assigned in FNR from Cyanidium caldarium, eukaryotic primitive red alga, with phycobilisomes on the surface of thylakoid membranes. We cloned FNR cDNA from Cyanidium caldarium by 5^' and 3^' RACE PCR method, and determined the deduced sequence. It had no CpcD-like domain but signal sequence targeting to chloroplast, and indicated 63.3 % identity to FNR from Nicotiana tobacum, 58.7 % to FNR from Cyanophora paradoxa and 44.9 % to FNR from Chlamydomonas reinhardtii in the catalytic domains, and no homology to these FNRs in the signal sequence region. These results suggest that the association of FNR on phycobilisome is not essential to FNR function. W. M. Schluchter and D. A. Bryant (1992) Biochemistry 31: 3092-3102 M. Nakajima et al. (2002) Plant Cell Physiol. 43(5): 484-493