大肠杆菌seqa蛋白质结构与功能-中国细胞生物学学报.pdfVIP

中国细胞生物学学报 Chinese Journal of Cell Biology 2016, 38(6): 72 1–728 DOI: 10.11844/cj cb.2016.06.0399 综述 大肠杆菌SeqA蛋白质结构与功能 乌日汗 梁 燕 李 静 莫日根* ( 内蒙古大学生命科学学院, 呼和浩特01002 1) 摘要 大肠杆菌SeqA蛋白质是染色体复制起始负调控因子。在体内, SeqA主要以四聚体或 多聚体形式存在, 有N-端多聚化结构域和C-端DNA结合结构域。大肠杆菌复制原点(the origin of Escherichia coli oriC oriC replication of the chromosome, )有11个GATC位点, 新复制的 处于半甲基化 状态, 其中相邻的两个半甲基化GATC是SeqA特异性结合靶位点。SeqA通过结合新复制的半甲基 oriC oriC oriC 化 来抑制复制起重新发生, 从而使 隔绝(sequestration) 。由SeqA介导的 隔绝是抑制同一 个细胞周期中复制起始重新发生的机制之一。SeqA不仅是复制起始调控因子, 也是一个转录因子, 抑制或激活一些基因的表达。该文就SeqA蛋白质的结构与功能域特点, 对DNA复制起始和基因表 达调控机制以及细胞分裂中的作用作一综述。 关键词 SeqA蛋白质; 结构与功能域; DNA复制起始; 隔绝 Structure and Function of the Escherichia coli SeqA Protein Wurihan, Liang Yan, Li Jing, Morigen* (School of Life Sciences, Inner Mongolia University, Hohhot 010021, China) Abstract The SeqA protein is a negative factor for initiation of chromosomal replication in Escherichia coli. In vivo the SeqA molecules are found in a form of tetramer or multimers. The SeqA protein has the N-terminal ag- gregation and the C-terminal DNA-binding domains. The E. coli chromosomal origin for replication (oriC) contains 11 GATC sites and newly replicated oriC is hemimethylated. The site of two neighboured hemimethylated GATC is the best target of SeqA for binding. SeqA binds to hemimthylated GATC to prevent re-initiation of replication, namely the sequestration of oriC. Sequestration is one of the mechanisms to make sure that each origin is initiated only once per cell cycle. The SeqA protein is not only a regulatory factor for replication initiatio