Vissers S, Andre B, Muyldermans F, Grenson M
Laboratoire de Microbiologie, Faculté des Sciences, Université Libre de Bruxelles, Belgium.
Eur J Biochem. 1989 May 1;181(2):357-61. doi: 10.1111/j.1432-1033.1989.tb14732.x.
In Saccharomyces cerevisiae, the pathway of 4-aminobutyric acid catabolism, for use as a nitrogen source, involves a specific permease (encoded by the UGA4 gene) and two enzymes (encoded by the UGA1 and UGA2 genes, respectively). The synthesis of these proteins is induced by 4-aminobutyrate. It also requires the product of the UGA3 gene. Here, we describe four additional regulatory mutations which provide evidence for the existence of both positive and negative regulatory elements which control the final expression of the UGA4 gene. Some of them simultaneously control the expression of the UGA1 and UGA2 genes. Three classes of mutant with a constitutive 4-aminobutyrate-specific permease have been isolated. (a) Recessive mutations in the UGA43 gene suggest that the product of the UGA43 gene behaves like a trans-acting negative regulator of UGA4 gene expression. (b) The semi-dominant mutation (uga11), closely linked to the UGA4 gene, might affect the receptor of the UGA43 gene product. In these two classes of mutant, only the permease is constitutive. (3) The uga81 mutation, closely linked to the UGA3 gene, makes the whole UGA regulon constitutive. On the other hand, recessive mutations at the UGA35 gene locus lead to non-inducibility of the UGA regulon. Hence the UGA35 gene product behaves like a second trans-acting positive regulator in addition to UGA3.
在酿酒酵母中，4-氨基丁酸分解代谢途径作为氮源使用时，涉及一种特定的通透酶（由UGA4基因编码）和两种酶（分别由UGA1和UGA2基因编码）。这些蛋白质的合成由4-氨基丁酸诱导。它还需要UGA3基因的产物。在此，我们描述了另外四个调控突变，这些突变提供了证据，证明存在控制UGA4基因最终表达的正调控元件和负调控元件。其中一些突变同时控制UGA1和UGA2基因的表达。已分离出三类具有组成型4-氨基丁酸特异性通透酶的突变体。(a) UGA43基因中的隐性突变表明，UGA43基因的产物表现为UGA4基因表达的反式作用负调控因子。(b) 与UGA4基因紧密连锁的半显性突变（uga11）可能影响UGA43基因产物的受体。在这两类突变体中，只有通透酶是组成型的。(3) 与UGA3基因紧密连锁的uga81突变使整个UGA操纵子组成型表达。另一方面，UGA35基因位点的隐性突变导致UGA操纵子不可诱导。因此，UGA35基因的产物除了UGA3之外，还表现为第二种反式作用正调控因子。
