Chasman D I, Kornberg R D
Department of Cell Biology, Stanford University School of Medicine, California 94305-5400.
Mol Cell Biol. 1990 Jun;10(6):2916-23. doi: 10.1128/mcb.10.6.2916-2923.1990.
Expression of the yeast Saccharomyces cerevisiae GAL4 protein under its own (galactose-inducible) control gave 5 to 10 times the level of protein observed when the GAL4 gene was on a high-copy plasmid. Purification of GAL4 by a procedure including affinity chromatography on a GAL4-binding DNA column yielded not only GAL4 but also a second protein, shown to be GAL80 by its reaction with an antipeptide antibody. Sequence comparisons of GAL4 and other members of a family of proteins sharing homologous cysteine finger motifs identified an additional region of homology in the middle of these proteins shown by genetic analysis to be important for GAL4 function. GAL4 could be cleaved proteolytically at the boundary of the conserved region, defining internal and carboxy-terminal folded domains.
酵母酿酒酵母GAL4蛋白在其自身（半乳糖诱导型）调控下的表达量是当GAL4基因位于高拷贝质粒上时所观察到的蛋白水平的5至10倍。通过在GAL4结合DNA柱上进行亲和层析等步骤纯化GAL4，不仅得到了GAL4，还得到了第二种蛋白，通过其与抗肽抗体的反应证明该蛋白是GAL80。对GAL4以及共享同源半胱氨酸指基序的蛋白质家族的其他成员进行序列比较，在这些蛋白质中间确定了一个额外的同源区域，通过遗传分析表明该区域对GAL4功能很重要。GAL4可以在保守区域的边界处被蛋白酶切割，从而界定内部和羧基末端折叠结构域。
