Morsy Fatthy Mohamed, Nakajima Masato, Yoshida Takayuki, Fujiwara Tatsuki, Sakamoto Toshio, Wada Keishiro
Division of Life Science, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa, 920-1192, Japan.
Photosynth Res. 2008 Jan;95(1):73-85. doi: 10.1007/s11120-007-9235-4. Epub 2007 Sep 9.
Ferredoxin-NADP(+) oxidoreductase (FNR) catalyzing the terminal step of the linear photosynthetic electron transport was purified from the cyanobacterium Spirulina platensis and the red alga Cyanidium caldarium. FNR of Spirulina consisted of three domains (CpcD-like domain, FAD-binding domain, and NADP(+)-binding domain) with a molecular mass of 46 kDa and was localized in either phycobilisomes or thylakoid membranes. The membrane-bound FNR with 46 kDa was solublized by NaCl and the solublized FNR had an apparent molecular mass of 90 kDa. FNR of Cyanidium consisted of two domains (FAD-binding domain and NADP(+)-binding domain) with a molecular mass of 33 kDa. In Cyanidium, FNR was found on thylakoid membranes, but there was no FNR on phycobilisomes. The membrane-bound FNR of Cyanidium was not solublized by NaCl, suggesting the enzyme is tightly bound in the membrane. Although both cyanobacteria and red algae are photoautotrophic organisms bearing phycobilisomes as light harvesting complexes, FNR localization and membrane-binding characteristics were different. These results suggest that FNR binding to phycobilisomes is not characteristic for all phycobilisome retaining oxygenic photosynthetic organisms, and that the rhodoplast of red algae had possibly originated from a cyanobacterium ancestor, whose FNR lacked the CpcD-like domain.
铁氧化还原蛋白-NADP(+)氧化还原酶（FNR）催化线性光合电子传递的末端步骤，该酶从蓝藻钝顶螺旋藻和红藻嗜热栖热放线菌中纯化得到。钝顶螺旋藻的FNR由三个结构域（类CpcD结构域、FAD结合结构域和NADP(+)结合结构域）组成，分子量为46 kDa，定位于藻胆体或类囊体膜中。分子量为46 kDa的膜结合FNR可被NaCl溶解，溶解后的FNR表观分子量为90 kDa。嗜热栖热放线菌的FNR由两个结构域（FAD结合结构域和NADP(+)结合结构域）组成，分子量为33 kDa。在嗜热栖热放线菌中，FNR存在于类囊体膜上，但藻胆体上没有FNR。嗜热栖热放线菌的膜结合FNR不能被NaCl溶解，这表明该酶紧密结合于膜中。尽管蓝藻和红藻都是以藻胆体作为光捕获复合体的光合自养生物，但FNR的定位和膜结合特性却有所不同。这些结果表明，FNR与藻胆体的结合并非所有保留藻胆体的产氧光合生物的特征，红藻的红质体可能起源于蓝藻祖先，其FNR缺乏类CpcD结构域。
