SOS反应(SOS response)也称应急反应,是对DNA损伤的整体反应,其中细胞周期被阻止,DNA修复和诱变(英语:Mutagenesis)被诱导。该系统涉及 RecA(英语:RecA) 蛋白(真核生物中的RAD51)。 RecA 蛋白受单链DNA刺激,参与SOS反应基因阻遏蛋白 (LexA(英语:LexA)) 的失活,从而诱导反应。它是一种容易出错的修复系统,对在广泛的物种中观察到的 DNA 变化有重大贡献。
E. coli SOS System: DNA can be damaged by cross-linking agents, UV irradiation, alkylating agents, etc. Once damaged, RecA, a LexA protease, senses that damaged DNA and becomes activated by removing its repressor. Once the LexA dimer repressor is removed, the expression of LexA operon is autoregulatory. In addition to being a LexA protease, the RecA protein also catalyzes a few novel DNA reactions such as annealing of single-stranded DNA and transfer of strands. The SOS system has enhanced DNA-repair capacity, including excision and post-replication repair, enhanced mutagenesis, prophage induction. The system can also inhibit cell division and cell respiration.[1]The SOS response has been proposed as a model for bacterial evolution of certain types of antibiotic resistance.[2]