Heterotrimerization of PII-like signalling proteins:: implications for PII-mediated signal transduction systems
Heterotrimerization of PII-like signalling proteins:: implications for PII-mediated signal transduction systems
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DOI：
10.1046/j.1365-2958.1999.01477.x
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发表时间：
1999-07-01
影响因子：
3.6
通讯作者：
Weiss, V
中科院分区：
文献类型：
--
作者：
Forchhammer, K;Hedler, A;Weiss, V
P-II样信号分子是由glnB基因家族编码的12-13 kDa多肽组成的三聚体蛋白。蓝藻glnB基因在大肠杆菌中的异源表达导致大肠杆菌失活。大肠杆菌自身的P-II信号系统。在目前的工作中，我们表明，这种影响是由蓝藻glnB基因产物和大肠杆菌之间形成功能上无活性的异源三聚体引起的。coli P-II旁系同源物GlnB和GlnK。这导致了E.大肠杆菌也彼此形成异源三聚体。使用聚球藻P-II蛋白的异源三聚化研究了寡聚化伴侣对单个亚基功能的影响。GlnB和GlnK的尿苷酰化效率较低，但在这些异源三聚体中仍然是可能的。相比之下，GlnB-UMP刺激GlnE（谷氨酰胺合成酶腺苷酰转移酶/去除酶）的腺苷酰去除活性的能力几乎完全被消除，证实了在氮逐步减少时谷氨酰胺合成酶的快速去腺苷酰化需要功能性同源三聚体GlnB蛋白。然而，值得注意的是，在将氮饥饿的细胞暴露于铵时，谷氨酰胺合成酶的快速腺苷酸化显示在功能性GlnB/GlnK信号传导系统不存在的情况下与在其存在下一样有效地发生。
P-II-like signalling molecules are trimeric proteins composed of 12-13 kDa polypeptides encoded by the glnB gene family. Heterologous expression of a cyanobacterial glnB gene in Escherichia coli leads to an inactivation of E. coli's own P-II signalling system. In the present work, we show that this effect is caused by the formation of functionally inactive heterotrimers between the cyanobacterial glnB gene product and the E. coli P-II paralogues GlnB and GlnK. This led to the discovery that GlnK and GlnB of E. coli also form heterotrimers with each other. The influence of the oligomerization partner on the function of the single subunit was studied using heterotrimerization with the Synechococcus P-II protein. Uridylylation of GlnB and GlnK was less efficient but still possible within these heterotrimers. In contrast, the ability of GlnB-UMP to stimulate the adenylyl-removing activity of GlnE (glutamine synthetase adenylyltransferase/removase) was almost completely abolished, confirming that rapid deadenylylation of glutamine synthetase upon nitrogen stepdown requires functional homotrimeric GlnB protein. Remarkably, however, rapid adenylylation of glutamine synthetase upon exposing nitrogen-starved cells to ammonium was shown to occur in the absence of a functional GlnB/GlnK signalling system as efficiently as in its presence.