Forchhammer K, Tandeau de Marsac N
Département de Biochimie et Génétique Moléculaire, Institut Pasteur, Paris, France.
J Bacteriol. 1995 Apr;177(8):2033-40. doi: 10.1128/jb.177.8.2033-2040.1995.
The PII protein (glnB gene product) in the cyanobacterium Synechococcus sp. strain PCC 7942 signals the cellular N status by being phosphorylated or dephosphorylated at a seryl residue. Here we show that the PII-modifying system responds to the activity of ammonium assimilation via the glutamine synthase-glutamate synthase pathway and to the state of CO2 fixation. To identify possible functions of PII in this microorganism, a PII-deficient mutant was created and its general phenotype was characterized. The analysis shows that the PII protein interferes with the regulation of enzymes required for nitrogen assimilation, although ammonium repression is still detectable in the PII-deficient mutant. We suggest that the phosphorylation and dephosphorylation of PII are part of a complex signal transduction network involved in global nitrogen control in cyanobacteria. In this regulatory process, PII might be involved in mediating the tight coordination between carbon and nitrogen assimilation.
在蓝藻聚球藻属菌种PCC 7942中，PII蛋白（glnB基因产物）通过丝氨酸残基的磷酸化或去磷酸化来传递细胞内的氮状态。我们在此表明，PII修饰系统对经由谷氨酰胺合成酶-谷氨酸合成酶途径的铵同化活性以及二氧化碳固定状态作出响应。为了确定PII在这种微生物中的可能功能，构建了一个PII缺陷型突变体并对其一般表型进行了表征。分析表明，PII蛋白干扰氮同化所需酶的调控，尽管在PII缺陷型突变体中仍可检测到铵阻遏。我们认为，PII的磷酸化和去磷酸化是参与蓝藻全局氮控制的复杂信号转导网络的一部分。在这个调控过程中，PII可能参与介导碳同化和氮同化之间的紧密协调。
