变异鱼腥藻
蓝藻
铁氧还蛋白
铁氧还蛋白NADP(+)还原酶
生物
鱼腥藻
异位囊肿
联合囊肿
藻胆体
生物化学
类囊体
叶绿体
藻蓝蛋白
光合作用
还原酶
质体蓝素
光系统I
酶
细菌
光系统II
基因
遗传学
作者
Felipe Alcántara-Sánchez,Lourdes Elizabeth Leyva-Castillo,Alicia Chagolla-López,Luis E. González de la Vara,Carlos Gómez-Lojero
标识
DOI:10.1016/j.biocel.2017.02.004
摘要
Ferredoxin-NADP+ reductase (FNR) transfers reducing equivalents between ferredoxin and NADP(H) in the photosynthetic electron transport chains of chloroplasts and cyanobacteria. In most cyanobacteria, FNR is coded by a single petH gene. The structure of FNR in photosynthetic organisms can be constituted by FAD-binding and NADPH-binding domains (FNR-2D), or by these and an additional N-terminal domain (FNR-3D). In this article, biochemical evidence is provided supporting the induction of FNR-2D by iron or combined nitrogen deficiency in the cyanobacteria Synechocystis PCC 6803 and Anabaena variabilis ATCC 29413. In cell extracts of these cyanobacteria, most of FNR was associated to phycobilisomes (PBS) or phycocyanin (PC), and the rest was found as free enzyme. Free FNR activity increased in both cyanobacteria under iron stress and during diazotrophic conditions in A. variabilis. Characterization of FNR from both cyanobacteria showed that the PBS-associated enzyme was FNR-3D and the free enzyme was mostly a FNR-2D isoform. Predominant isoforms in heterocysts of A. variabilis were FNR-2D; where its N-terminal sequence lacked an initial (formyl)methionine. This means that FNR-3D is targeted to thylakoid membrane, and anchored to PBS, and FNR-2D is found as a soluble protein in the cytoplasm, when iron or fixed nitrogen deficiencies prevail in the environment. Moreover, given that Synechocystis and Anabaena variabilis are dissimilar in genotype, phenotype and ecology, the presence of these two-domain proteins in these species suggests that the mechanism of FNR induction is common among cyanobacteria regardless of their habitat and morphotype.
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