Petit M A, Ehrlich S D
Laboratoire de Génétique Microbienne, INRA, 78352 Jouy en Josas, France.
Nucleic Acids Res. 2000 Dec 1;28(23):4642-8. doi: 10.1093/nar/28.23.4642.
DNA ligases are grouped into two families, ATP-dependent and NAD-dependent, according to the cofactor required for their activity. A surprising capability of both kinds of ligases to complement for one another in vivo has been observed. Bacillus subtilis harbours one NAD-dependent ligase, YerG, and two ATP-dependent ligases, YkoU and YoqV, this last one being encoded by the 134 kb lysogenic bacteriophage SPss and consisting of a single adenylation domain typical of ATP-dependent ligases. Because the genetics of ligases in B.subtilis had not been studied previously, the genes encoding for one ligase of each kind, yerG and yoqV, were investigated. We found that the yerG gene was essential in B.subtilis. This suggests that none of the ATP-dependent ligases was able to complement the yerG defect. In addition, the ATP-dependent ligase encoded by yoqV, when cloned on a plasmid under appropriate expression signals, was unable to rescue a yerG mutant strain. The two B.subtilis ligase genes yerG and yoqV were also introduced in an Escherichia coli strain encoding a thermosensitive ligase (ligts), and whereas yoqV did not complement the ligts defects, yerG fully complemented the growth and UV sensitivity defects of the lig mutant. We propose to rename the yerG and yoqV genes of B.subtilis ligA and ligB respectively.
DNA连接酶根据其活性所需的辅因子分为两个家族，即ATP依赖性和NAD依赖性。已经观察到两种连接酶在体内具有令人惊讶的相互互补能力。枯草芽孢杆菌含有一种NAD依赖性连接酶YerG和两种ATP依赖性连接酶YkoU和YoqV，后者由134 kb的溶原性噬菌体SPss编码，由ATP依赖性连接酶典型的单个腺苷化结构域组成。由于之前尚未研究过枯草芽孢杆菌中连接酶的遗传学，因此对编码每种连接酶的基因yerG和yoqV进行了研究。我们发现yerG基因在枯草芽孢杆菌中是必需的。这表明没有一种ATP依赖性连接酶能够弥补yerG缺陷。此外，由yoqV编码的ATP依赖性连接酶，当在适当的表达信号下克隆到质粒上时，无法挽救yerG突变菌株。枯草芽孢杆菌的两个连接酶基因yerG和yoqV也被导入编码热敏连接酶（ligts）的大肠杆菌菌株中，虽然yoqV不能弥补ligts缺陷，但yerG完全弥补了lig突变体的生长和紫外线敏感性缺陷。我们建议将枯草芽孢杆菌的yerG和yoqV基因分别重新命名为ligA和ligB。
