Mazzoni C, Saliola M, Falcone C
Department of Cell and Developmental Biology, University of Rome, La Sapienza, Italy.
Mol Microbiol. 1992 Aug;6(16):2279-86. doi: 10.1111/j.1365-2958.1992.tb01403.x.
The alcohol dehydrogenase (ADH) system in the yeast Kluyveromyces lactis is encoded by four ADH genes. In this paper we report evidence that at least three of these genes are transcribed and translated into protein. KIADH1 and KIADH2, which encode cytoplasmic activities, are preferentially expressed in glucose-grown cells with respect to ethanol-grown cells. KIADH4, which encodes one of the two activities localized within mitochondria, is induced at the transcriptional level in the presence of ethanol as is the ADH2 gene in Saccharomyces cerevisiae. However the regulation of the expression of the K. lactis gene is completely different from that of ADH2 and of other known ADH genes in that KIADH4 is insensitive to glucose repression and is not expressed on non-fermentable carbon sources other than ethanol. This kind of regulation can be clearly observed in non-fermenting strains, where the induction of KIADH4 is dependent on the addition of ethanol to the medium. On the contrary, in fermenting strains KIADH4 is always induced by ethanol or acetaldehyde produced endocellularly and this results in constitutive expression of the gene also in the presence of glucose. The mitochondrial localization of the activity encoded by KIADH4 and the peculiar regulation of this gene could be related to the fact that K. lactis is a petite negative yeast in which some mitochondrial functions seem to be essential for cell viability.
乳酸克鲁维酵母中的乙醇脱氢酶（ADH）系统由四个ADH基因编码。在本文中，我们报告了证据表明这些基因中至少有三个被转录并翻译成蛋白质。编码胞质活性的KIADH1和KIADH2相对于乙醇培养的细胞，在葡萄糖培养的细胞中优先表达。编码定位于线粒体的两种活性之一的KIADH4在乙醇存在下在转录水平上被诱导，就像酿酒酵母中的ADH2基因一样。然而，乳酸克鲁维酵母基因表达的调控与ADH2和其他已知ADH基因的调控完全不同，因为KIADH4对葡萄糖阻遏不敏感，并且在除乙醇以外的不可发酵碳源上不表达。这种调控在非发酵菌株中可以清楚地观察到，其中KIADH4的诱导依赖于向培养基中添加乙醇。相反，在发酵菌株中，KIADH4总是由细胞内产生的乙醇或乙醛诱导，这导致该基因在葡萄糖存在下也组成型表达。KIADH4编码的活性的线粒体定位以及该基因的特殊调控可能与乳酸克鲁维酵母是一种小菌落阴性酵母这一事实有关，在这种酵母中一些线粒体功能似乎对细胞活力至关重要。
