Razquin P, Fillat M F, Schmitz S, Stricker O, Böhme H, Gómez-Moreno C, Peleato M L
Departamento de Bioquímica y Biología Molecular y Cellular, Facultad de Ciencias, Universidad de Zaragoza, Spain.
Biochem J. 1996 May 15;316 ( Pt 1)(Pt 1):157-60. doi: 10.1042/bj3160157.
The expression of ferredoxin-NADP+ reductase (FNR) from Anabaena sp. PCC 7119 in heterocysts and vegetative cells has been quantified. Specific reductase activity in heterocysts was approximately 10 times higher than in vegetative cells, corresponding to the increased FNR protein content. This was confirmed by immunoquantification of the FNR protein from whole filaments of Anabaena sp. PCC 7120 grown in media with and without combined nitrogen. Transcription of the petH gene was markedly enhanced in the absence of combined nitrogen. This suggests that the increased RNA level is mainly responsible for the up-regulation of FNR in heterocysts. As has been observed for nif genes, iron deficiency also increased transcription of petH. Characterization of the FNR purified from isolated heterocysts showed no detectable differences from the enzyme from vegetative cells. Although nitrogen stress was a key regulatory factor, localization of the petH gene in the genomic map of Anabaena PCC 7120 showed that this gene is not physically associated with the nif cluster.
已对鱼腥藻PCC 7119的铁氧化还原蛋白-NADP⁺还原酶（FNR）在异形胞和营养细胞中的表达进行了定量。异形胞中的特异性还原酶活性比营养细胞中高约10倍，这与FNR蛋白含量的增加相对应。这通过对在含和不含化合态氮的培养基中生长的鱼腥藻PCC 7120的整个丝状体中的FNR蛋白进行免疫定量得以证实。在没有化合态氮的情况下，petH基因的转录显著增强。这表明RNA水平的增加主要是异形胞中FNR上调的原因。正如在固氮基因中所观察到的，缺铁也会增加petH的转录。从分离的异形胞中纯化的FNR的特性表明，它与营养细胞中的酶没有可检测到的差异。尽管氮胁迫是一个关键的调节因子，但petH基因在鱼腥藻PCC 7120基因组图谱中的定位表明，该基因在物理上与固氮基因簇不相关。
