Julien B, Calendar R
Department of Molecular and Cell Biology, University of California, Berkeley, USA.
J Bacteriol. 1995 Jul;177(13):3743-51. doi: 10.1128/jb.177.13.3743-3751.1995.
The bacteriophage P4 delta protein is a transcriptional activator of the late genes of P4 as well as the late genes of its helpers, such as bacteriophage P2. delta was purified, using a variation of the MalE fusion system. With this method we purified two forms of delta: a fusion of MalE and delta and a unfused form. The fusion by itself is not active in vivo or in vitro, but the mixture of the fusion and the unfused delta is active in both. Using nitrocellulose filtration and gel mobility shift assays, we show that delta binds DNA, and using DNase I footprinting, we show that delta binds to sequences centered at approximately -55 in the two late promoters of P4 as well as the four late promoters of its helper P2. In addition, the P4 sid promoter contains a second delta binding site centered at -18.
噬菌体P4 δ蛋白是P4晚期基因及其辅助噬菌体（如噬菌体P2）晚期基因的转录激活因子。利用麦芽糖结合蛋白（MalE）融合系统的一种变体对δ进行了纯化。通过这种方法，我们纯化出了两种形式的δ：MalE与δ的融合体以及未融合形式。该融合体自身在体内或体外均无活性，但融合体与未融合的δ的混合物在两者中均有活性。通过硝酸纤维素过滤和凝胶迁移率变动分析，我们发现δ能结合DNA，而通过DNA酶I足迹法，我们发现δ结合于P4两个晚期启动子以及其辅助噬菌体P2的四个晚期启动子中位于大约-55处的序列中心。此外，P4 sid启动子含有第二个位于-18处的δ结合位点。
