Nozaki Shingo, Ogawa Tohru
Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan.
Microbiology (Reading). 2008 Nov;154(Pt 11):3379-3384. doi: 10.1099/mic.0.2008/019745-0.
The DnaA protein is the bacterial initiator of replication at a unique chromosomal site, oriC. It is present in all bacterial species and has a conserved structure with four domains. The structures of domains I and III-IV have been solved recently for some bacterial species, and the molecular process leading to the initiation event has been investigated in detail. On the other hand, domain II appears to have no rigid structure and is assumed to be a flexible linker connecting the N-terminal domain I and the C-terminal domains III-IV. It differs significantly in length and amino acid sequence among bacterial species. Whether or not domain II has any function(s) to initiate replication is unknown. The precise borders at both of its ends as well as its essential portions for cell viability are also unknown. In this study, we introduced systematic deletions into the domain II region on the chromosomal dnaA gene of Escherichia coli and examined their effect on cell physiology. Stretches of 30-36 consecutive amino acid residues could be deleted from various portions between the 78th and the 136th residues without affecting cell viability. We propose that domain II of E. coli DnaA is from the 79th to the 135th residues and at least 21-27 residues are required as a spacer to keep domains I and III-IV in the correct positions.
DnaA蛋白是细菌在独特的染色体位点oriC处的复制起始因子。它在所有细菌物种中都存在，具有由四个结构域组成的保守结构。最近已解析了一些细菌物种中结构域I和III - IV的结构，并对导致起始事件的分子过程进行了详细研究。另一方面，结构域II似乎没有刚性结构，被认为是连接N端结构域I和C端结构域III - IV的柔性接头。它在细菌物种之间的长度和氨基酸序列差异很大。结构域II是否具有启动复制的任何功能尚不清楚。其两端的精确边界以及对细胞活力至关重要的部分也不清楚。在本研究中，我们对大肠杆菌染色体dnaA基因上的结构域II区域进行了系统性缺失，并研究了它们对细胞生理学的影响。在第78至136个残基之间的各个部分可以删除30 - 36个连续的氨基酸残基片段，而不影响细胞活力。我们提出大肠杆菌DnaA的结构域II是从第79至135个残基，并且至少需要21 - 27个残基作为间隔物，以将结构域I和III - IV保持在正确位置。
