A rationale for autoinduction of a transcriptional activator: ethanolamine ammonia-lyase (EutBC) and the operon activator (EutR) compete for adenosyl-cobalamin in Salmonella typhimurium.
A rationale for autoinduction of a transcriptional activator: ethanolamine ammonia-lyase (EutBC) and the operon activator (EutR) compete for adenosyl-cobalamin in Salmonella typhimurium.
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转录激活剂自诱导的基本原理：乙醇胺解氨酶 (EutBC) 和操纵子激活剂 (EutR) 在鼠伤寒沙门氏菌中竞争腺苷钴胺素。
DOI：
10.1128/jb.176.5.1287-1296.1994
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发表时间：
1994
影响因子：
3.2
通讯作者：
Roth,JR
中科院分区：
文献类型：
--
作者：
Sheppard,DE;Roth,JR
鼠伤寒沙门氏菌的乙醇胺利用（eut）操纵子由一种正调控蛋白（EutR）控制，该蛋白刺激eut操纵子表达，以响应同时存在的两种效应物，乙醇胺和腺苷钴胺素（EUT-B12）。B12是乙醇胺氨裂解酶（裂解酶）的辅因子，乙醇胺降解途径中的第一种酶。Eut操纵子诱导过程中，该途径依赖于EUT-B12作为效应子的使用，这可以通过EUT-B12在乙醇胺降解中的作用以及该辅因子并不总是由S.鼠伤寒。eutR基因位于eut操纵子内，并且其自身诱导是最大操纵子表达所必需的。有证据表明，EutR调控基因的操纵子内的位置提供了一种手段，平衡裂解酶和调节蛋白之间的竞争，一个非常小的游泳池的EUT-B12。由于裂合酶和调节蛋白都被诱导，它们可以更平等地竞争一小部分B12。这允许连续的eut操纵子诱导和裂解酶活性。两个一般性的意见支持这一模式。首先，突变，使裂解酶允许操纵子完全诱导的外源性钴胺素（CN-B12）比野生型操纵子所需的更低的水平。这种灵敏度的增加被测量为外源CN-B12对操纵子诱导的表观Km的降低。第二，过量CN-B12诱导操纵子的最大水平由EutR调节蛋白的水平决定，而与裂解酶的水平无关。
The ethanolamine utilization (eut) operon of Salmonella typhimurium is controlled by a positive regulatory protein (EutR) which stimulates eut operon expression in response to the simultaneous presence of two effectors, ethanolamine and adenosyl-cobalamin (Ado-B12). Ado-B12 is a cofactor for ethanolamine ammonia-lyase (lyase), the first enzyme in the ethanolamine-degradative pathway. The dependence of this pathway on the use of Ado-B12 as an effector in eut operon induction may be explained by its role in the degradation of ethanolamine and the fact that this cofactor is not always made by S. typhimurium. The eutR gene lies within the eut operon, and its autoinduction is required for maximum operon expression. Evidence is presented that the placement of the eutR regulatory gene within the operon provides a means of balancing the competition between lyase and the regulatory protein for a very small pool of Ado-B12. Since both lyase and the regulatory protein are induced, they can compete more equally for a small pool of Ado-B12. This permits both continued eut operon induction and lyase activity. Two general observations support this model. First, mutations that inactivate lyase allow the operon to be fully induced by a lower level of exogenous cobalamin (CN-B12) than required by a wild-type operon. This increase in sensitivity is measured as a reduction in the apparent Km for operon induction by exogenous CN-B12. Second, the maximum level of operon induction by excess CN-B12 is dictated by the level of EutR regulatory protein, regardless of the level of lyase.