Phosphoprotein PII from Cyanobacteria-猫眼课题宝

蓝藻磷蛋白 PII

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发表时间：

1997

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作者：

K. Forchhammer;A. Hedler

来自大肠杆菌的信号转导蛋白PII是通过尿苷基化修饰的，而来自蓝藻聚球藻PCC7942的信号转导蛋白PII是在丝氨酸残基上磷酸化的。为了阐明这些蛋白之间的功能保守性，我们比较了聚球藻PII蛋白和大肠杆菌PII蛋白的已知性质。与大肠杆菌蛋白相似，聚球藻PII以相互依赖的方式结合代谢产物2-氧戊二酸和三磷酸腺苷。对配体结合的协同效应进行了详细的分析。聚球藻PII的ATP结合部位可用5‘-对氟磺酰苯甲酰腺苷标记。通过蓝藻glnB基因在大肠杆菌中的异源表达，我们证明聚球藻PII可以被E.ColiPII尿苷基转移酶修饰。聚球藻PII的存在阻止了大肠杆菌PII到NtrB的信号转导，可能是通过非功能性竞争。因此，我们认为聚球藻PII的主要功能是感应2-氧代戊二酸，这是氮同化所需的碳骨架。

The signal transduction protein PII from Escherichia coli is modified by uridylylation, whereas its counterpart from the cyanobacterium Synechococcus PCC 7942 is phosphorylated at a seryl residue. To elucidate functional conservations between these proteins, we compared the Synechococcus PII protein with the known properties of the E. coli PII protein. Similar to the E. coli protein, Synechococcus PII binds the metabolites 2-oxoglutarate and ATP in a mutually dependent manner. The synergism of ligand binding was analyzed in detail. The ATP-binding site of Synechococcus PII could be labelled with 5′-p-fluorosulfonylbenzoyladenosine. By heterologous expression of the cyanobacterial glnB gene in E. coli we showed that Synechococcus PII can be modified by the E. coli PII uridylyltransferase. The presence of Synechococcus PII prevents signal transduction of E. coli PII to NtrB, presumably by non-functional competition. We therefore propose that the primary function of Synechococcus PII is to sense 2-oxoglutarate, the carbon skeleton required for nitrogen assimilation.