Wong K, Geiduschek E P
Department of Biology and Center for Molecular Genetics, University of California, 9500 Gilman Drive, San Diego, CA, 92093-0634, USA.
J Mol Biol. 1998 Nov 27;284(2):195-203. doi: 10.1006/jmbi.1998.2166.
Activation of transcription at bacteriophage T4 late promoters and coupling of late transcription to concurrent replication requires a peculiar transcriptional activator, the gp45 sliding clamp of the T4 DNA polymerase. In order to activate transcription, the topologically DNA-linked trimeric gp45 must interact with two T4-encoded RNA polymerase-binding proteins, the gp33 co-activator, and the gp55 late sigma factor. The carboxy termini of gp55 and gp33 share a similar sequence, which has been shown to be required for response of late transcription to activation by gp45. Alanine-scanning mutagenesis of the C terminus of gp55 shows that residues within the short hydrophobic sequence L(D/A)FLYE, are necessary for gp55 to bind to gp45, and to respond maximally to transcriptional activation by gp45. When fused to GST, the peptide SLDFLYE suffices for specific gp45 binding. Thus, it constitutes the main gp55 epitope for gp45 interaction.
噬菌体T4晚期启动子转录的激活以及晚期转录与同时进行的复制的偶联需要一种特殊的转录激活因子，即T4 DNA聚合酶的gp45滑动夹。为了激活转录，拓扑学上与DNA相连的三聚体gp45必须与两种T4编码的RNA聚合酶结合蛋白相互作用，即gp33共激活因子和gp55晚期σ因子。gp55和gp33的羧基末端具有相似的序列，已证明该序列是晚期转录对gp45激活作出反应所必需的。对gp55 C末端进行丙氨酸扫描诱变表明，短疏水序列L(D/A)FLYE内的残基是gp55与gp45结合以及对gp45转录激活作出最大反应所必需的。当与GST融合时，肽段SLDFLYE足以实现与gp45的特异性结合。因此，它构成了gp55与gp45相互作用的主要表位。
