Salmeron J M, Leuther K K, Johnston S A
Department of Botany, Duke University, Durham, North Carolina 27706.
Genetics. 1990 May;125(1):21-7. doi: 10.1093/genetics/125.1.21.
The carboxy-terminal 28 amino acids of the Saccharomyces cerevisiae transcriptional activator protein GAL4 execute two functions--transcriptional activation and interaction with the negative regulatory protein, GAL80. Here we demonstrate that these two functions are separable by single amino acid changes within this region. We determined the sequences of four GAL4C-mutations, and characterized the abilities of the encoded GAL4C proteins to activate transcription of the galactose/melibiose regulon in the presence of GAL80 and superrepressible GAL80S alleles. One of the GAL4C mutations can be compensated by a specific GAL80S mutation, resulting in a wild-type phenotype. These results support the idea that while the GAL4 activation function tolerates at least minor alterations in the GAL4 carboxyl terminus, the GAL80-interactive function is highly sequence-specific and sensitive even to single amino acid alterations. They also argue that the GAL80S mutations affect the affinity of GAL80 for GAL4, and not the ability of GAL80 to bind inducer.
酿酒酵母转录激活蛋白GAL4的羧基末端28个氨基酸执行两种功能——转录激活以及与负调控蛋白GAL80相互作用。我们在此证明，通过该区域内的单个氨基酸变化可将这两种功能分开。我们确定了四个GAL4C突变的序列，并表征了编码的GAL4C蛋白在存在GAL80和超抑制性GAL80S等位基因的情况下激活半乳糖/蜜二糖调节子转录的能力。其中一个GAL4C突变可被特定的GAL80S突变补偿，从而产生野生型表型。这些结果支持以下观点：虽然GAL4激活功能可容忍GAL4羧基末端至少有微小改变，但GAL80相互作用功能具有高度序列特异性，甚至对单个氨基酸改变也很敏感。它们还表明，GAL80S突变影响GAL80对GAL4的亲和力，而不影响GAL80结合诱导剂的能力。
