The two opposing activities of adenylyl transferase reside in distinct homologous domains, with intramolecular signal transduction
The two opposing activities of adenylyl transferase reside in distinct homologous domains, with intramolecular signal transduction
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DOI：
10.1093/emboj/16.18.5562
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发表时间：
1997-09-15
期刊：
影响因子：
11.4
通讯作者：
Vasudevan, SG
中科院分区：
文献类型：
--
作者：
Jaggi, R;vanHeeswijk, WC;Vasudevan, SG
腺苷酸转移酶（ATase）是大肠杆菌氮同化级联中的双功能效应酶，控制谷氨酰胺合成酶（GS）的活性。本研究解决了ATase的两种拮抗活性（腺苷化和去烯化）是否发生在相同或不同的活性位点的问题。945氨基酸残基ATase有两种截断方式，从而产生对应于氨基酸1-423 （AT-N）和425-945 （AT-C）的两个同源多肽。我们证明ATase有两个活性位点；AT-N具有去氧基化活性，AT-C具有腺苷基化活性。谷氨酰胺激活AT-C结构域的腺苷化反应，而α -酮戊二酸激活AT-N结构域催化的去烯化反应。然而，对于氮状态监控器PII的调控，腺苷化结构域似乎依赖于死基化结构域：AT-N的死基化活性依赖于PII- ump，并被PII抑制。AT-C的腺苷化活性与PII（或PII- ump）无关，而在完整的酶中，这种活性需要PII。讨论了这种分子内信号转导对预防无效循环的影响。
Adenylyl transferase (ATase) is the bifunctional effector enzyme in the nitrogen assimilation cascade that controls the activity of glutamine synthetase (GS) in Escherichia coli. This study addresses the question of whether the two antagonistic activities of ATase (adenylylation and deadenylylation) occur at the same or at different active sites. The 945 amino acid residue ATase has been truncated in two ways, so as to produce two homologous polypeptides corresponding to amino acids 1-423 (AT-N) and 425-945 (AT-C). We demonstrate that ATase has two active sites; AT-N carries a deadenylylation activity and AT-C carries an adenylylation activity. Glutamine activates the adenylylation reaction of the AT-C domain, whereas alpha-ketoglutarate activates the deadenylylation reaction catalysed by the AT-N domain. With respect to the regulation by the nitrogen status monitor PII, however, the adenylylation domain appears to be dependent on the deadenylylation domain: the deadenylylation activity of AT-N depends on PII-UMP and is inhibited by PII. The adenylylation activity of AT-C is independent of PII (or PII-UMP), whereas in the intact enzyme PII is required for this activity. The implications of this intramolecular signal transduction for the prevention of futile cycling are discussed.